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Admiral Biscuit


"This was quite well written, and the characters had a very natural feeling back and forth. Shame I didn't like it at all."

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Aug
20th
2019

Mechanic: Lacking Information · 1:21am Aug 20th, 2019

For this one, we’re gonna talk about a vehicle I should know well: a Dodge Caravan.


Now Kiss

This particular vehicle didn’t have functioning air conditioning.


All in all, it was a basic Caravan. 2005 or thereabouts, it had rear AC and dual zone in the front, which was the most common configuration--all three of mine are set up that way. It had an overhead console with the display, which is important later.

I didn’t do the initial diagnosis on it. My manager had looked at it. He told me that he’d checked the refrigerant pressure with the AC machine, and it was sufficient for the AC compressor on the vehicle to turn on. He’d also hooked the scan tool up to it, and the sensor on the vehicle also indicated sufficient pressure.

A lot of computer controlled components can be turned on and off with the scan tool, and such was the case with the AC compressor on these. He said that the scan tool would NOT turn on the AC, but if he jumpered the relay, the compressor did come on. He said that when he did, he could feel cold air blowing through the vents, and he also said that when he did the cooling fan did not come on.

There were no useful codes in either the engine control module, nor were there useful codes in the HVAC module.

So what we had, in short, was a vehicle that simply did not want to turn the AC on.


I’ll step away from the vehicle for just a second, to give you a basic, generic rundown of how modern vehicles control the AC system. Just the real basics.

Typically, there are two ways it turns on. One of them is the switch you push; like many functions on the car, that sends a request to a module to make something happen. In this case, the HVAC controller tells the PCM that you want AC, and if it’s appropriate, it’ll give it to you.

The other way is if you set the controls to defrost. Since clearing the windshield is aided by removing moisture, and since that’s one thing that AC does, all vehicles that I’m aware of that have AC typically turn it on when the vent control is set to defrost. Once again, the HVAC controller tells the PCM what it wants, and the PCM does it if it’s appropriate.

There are a few reason why it might not let you have AC. One is that the system is empty of freon; most modern cars have one or more pressure sensors in the system, and if it’s too low or too high, it won’t let you have AC.

Too much engine load, for whatever reason, could block the AC request. I’ve seen that before on a Suburban that was idling so low that to turn on the AC would stall the engine. The truck knew that, so it wouldn’t allow the AC compressor to turn on.

Another reason would be that it’s inappropriate. If, for some reason, you decided to turn the AC on max when it was below freezing outside, the car wouldn’t bother with AC since it can’t make the air coming through the vents colder than it already is.


Source

Finally, another likely cause would be some part of the drivetrain is overtemperature (engine or transmission), or the cooling fans can’t be controlled properly. In order to make cold inside the cabin, the AC system has to make hot in the engine compartment, and if it can’t shed that heat, pressures go really high and then things get interesting. The pressure relief valve on an AC system opening is loud and very messy, and it’s best to avoid it.

Once the system is operating, depending on the vehicle, there are various inputs which help control it. Very simply, the more load on the engine, the less fuel mileage you get, so designers want to keep the engine load down whenever they can. External temperature sensors, sunload sensors, in-cabin temperature sensors, evaporator temperature sensors, and various other devices are used, depending on the complexity of the system.

If your eyes glazed over there just a bit, our Caravan has a reasonably simple system, most of which can be monitored from an aftermarket scan tool.

Most.


Now that I’d been given the keys to the vehicle (literally), I wanted to do some initial checks of my own. It wasn’t that I didn’t mistrust my manager’s initial diagnosis, but I’m more familiar with these things than he is.

One of the first things to look for, if you can, is if the vehicle saw the AC request. Usually, that’s a data line that’s either yes or no. In this case, it was yes.

Then you see if the PCM wants to turn the AC on, which is another yes/no.

In this case, it was no.

So we already know several somethings. We know that the PCM knows that the AC has been requested, and we also know that the PCM isn’t allowing it to be turned on.

One thing that would be nice is if the scan tool said why, but that information is rarely given. Over the last decade, some of that has been added; for example, on many GM vehicles, they’ll tell you why the cruise control turned off the last ten times. Really handy for diagnosing cruise control complaints.

We don’t get that for the AC.

Just for giggles, I decided to make sure that the PCM could actually control the AC compressor. You’d think if it couldn’t, it would throw a code, but they don’t always. So I went into the functional tests screen, selected the AC compressor, and it worked.


Source

Which was odd, because my manager had said that it didn’t.

[Rather than rely on you remembering this later when I give the reveal, I’ll tell you right now that he ran the test wrong. He didn’t know that on these Chryslers, you can only run this test when the engine is off. He did it with the engine running, like you would on GM, and the vehicle simply ignored him.]

This verified a few things for me. The PCM was capable of seeing an AC request and acting on it. That meant that something was blocking it. Something that wouldn’t set a code, which likely meant it wasn’t actually a malfunction, but a deliberate thing.

This was also something I’d seen on Chrysler minivans before.

Remember that outside air temperature sensor I mentioned before? The one that won’t let the AC work if it’s too cold, because why bother with AC when it’s cold? And--I didn’t tell you this--but if the circuit’s open, it defaults to -40 (F or C, take your pick).

“But wait, Admiral,” you’re saying, because you’ve read lots of these. “Surely the computer knows that’s wrong. After the vehicle has been sitting for a period of time, it can compare the engine coolant temperature sensor and the intake air temperature sensor and the transmission fluid temperature sensor with the ambient air temperature sensor, and know that the odd man out has failed.”

And of course, you’re right. It can, and it does.

But.

Here’s the sneaky thing.

Lots of components that aren’t critical to engine functionality or aren’t expected to have to react rapidly just communicate with the physically closest module, which then sends the info on either a low or high speed bus to the modules which might care to have that information. The ambient air temperature sensor, which is located in the grille on the front bumper, is physically closest to the smart fuse box, so that’s who gets that information.

Now, you’d be right to imagine that the smart fuse box can report that something isn’t right with this sensor. I have no idea if it does or doesn’t, because the Snap On scan tool can’t communicate with that module. The last one I diagnosed with a malfunctioning OAT sensor was when we were testing out the Autel scan tool, which could.

However, as it happens, there’s a second module who sees this information, and I don’t even need a scan tool to determine what it’s seeing. The overhead computer displays outside temperature, which it gets from that very sensor, and in fact on this van, it was correct.

So there went that theory.


In fact, every single thing I monitored in the HVAC module was sensible, and indicated no reason why the AC might not work.


Source

The next thing we did was recharge the system, and I’m glad we did. It turned out to be undercharged, and while that didn’t fix its control problem, it gave us confidence that if we were to figure out what was blocking the AC, the system would turn on and function normally.

My next stop was Identifix. I typed in the symptoms--no AC--and started reading the results. Most of them weren’t helpful; most of them were things I’d already looked at and rejected. But there was one item that showed up on the list that I hadn’t checked, the evaporator temperature sensor.

The primary purpose of this would be to ensure that the evaporator wasn’t too cold--if it was, ice could accumulate, blocking airflow, and you wouldn’t get AC until the ice melted. Sure, it would be super-frigid in the depths of the HVAC plenum, but that only provides comfort to the mouse who’s made a nest on top of the cabin air filter.*

That knocked some gears loose in my brain. There was a data PID for that, and I hadn’t paid it much attention.

Well, it looked normal at first, but then when I started graphing it, things got weird. It said the temperature was okay, but the voltage was probably too low for that to be a normal value.

____________________________________________
*generally, the cabin air filter is before the evaporator, so the mouse wouldn’t actually get any cooling, either.


Most sensors on a vehicle operate on a 5 volt scale, and most of them only have valid values between 0.5V and 4.5V. Chopping off the high and low end is for reliability, it makes up for poor connections and the like. The evaporator temperature sensor was reading 0.03V, which is unlikely to be a valid reading.

More importantly, it’s not a sensible reading. Since the point of this thing is to make sure that the evaporator doesn’t freeze, one end of its scale should be somewhere around the freezing point, and the other end of its scale ought to be about as hot as Chrysler thinks this thing is likely to get. No matter what, the 70 degrees (F) it was displaying on the scan tool didn’t correlate with 0.03V. If I assume that this sensor is one of the exceptions to the half-volt buffer, I’d assume that 0V should either be as low as the sensor can read, or as high as it can read, and 70F shouldn’t be either of those values.

What I think is that the scan tool is showing me a generated value. The computer doesn’t know what the sensor is telling it, so it’s programmed to stuff in a default number and work with that.

Admittedly, that doesn’t entirely make sense, either; 70F should allow the AC to operate.

While the vehicle was running, the voltage jumped all over the place with no rhyme or reason. And when we manually operated the AC for short periods of time (using a jumper relay) it was no more reliable. Both the voltage and the temperature value on the scan tool changed randomly, and not always sensibly (if the air temperature coming out of the vent is 50F, I know that the evaporator can’t be hotter than that, because that’s not how physics works).

So we ordered one, and when it arrived, we just plugged it in to see what would happen. Which, incidentally, is less fun than it sounds.


Source

You’re supposed to remove the instrument panel to gain access to this little guy, ‘cause it’s basically directly behind the radio, under the dash pad. However, it turns out that with a little bit of ingenuity, a 90 degree drill, a boroscope, and a willingness to jam your arm into a tiny space without complete assurance you’ll get it back, you can change it without taking the instrument panel all the way out. Plus, now that we know where it is, and where wood blocks need to be wedged into the dash cover for clearance, we can change the next one quicker.


You’ll be happy to know that the AC worked perfectly after installing the new sensor, although I still wasn’t entirely happy with how the voltage displayed on the scan tool. The temperature graph looked just like you’d expect it to--it went from ambient air temperature down to about 40F when the AC was running.

The voltage graph did not please me, however. It went from about one volt down to about 0.5V, and then jumped up to 4.5V, whereupon it went down to around 4V.

I have no idea if that’s a malfunction in the scan tool, or if that’s actually how that temperature sensor is supposed to work for some odd reason, and I wasn’t curious enough to pull the dash partially apart to measure it myself with a multimeter. The point was that we’d made the PCM happy, and in a lot of cases, that’s what a repair is actually about.


So what’s the moral to this story? I dunno. Sometimes computers do things without telling you they’re doing them, and sometimes even a very expensive scan tool can’t provide you with all the information you wish you had. Sometimes you’ve just got to rely on experience to see something that doesn’t look right.


Source


Also, I decided today that I’m not gonna leave y’all with a pony pic as an outro (although the face smashy anonfilly is an appropriate way to end).

No, today, y’all get MUSIC.

Crank it to eleven for maximum effectiveness.

Comments ( 67 )

Heh. My parents had two Grand Caravans over the years - a 1995 SE and a 1999 Sport. (still miss that electric blue with the too silly not to get spoiler)

Both of them eventually ran into a similar issue with the AC not running for what would seem to be inexplicable reasons. If I recall, changing that same sensor fixed the 95 van. On the 99, the issue was eventually traced to short outs in the board that controlled the climate control buttons, so the dealer had to basically replace the entire center stack, since it was all one assembly.

Tiny pic, but it's the only one I could find on Google.

imganuncios.mitula.net/dodge_grand_caravan_1999_1999_dodge_grand_caravan_sport_4960119534684324124.jpg

Uses -40 so it doesnt have to select a correction function, and its effectively a failsafe value, shutting the system down instead of burning the compressor out?

This verified a few things for me. The PCM was capable of seeing and (an) AC request and acting on it. That meant that something was blocking it. Something that wouldn’t set a code, which likely meant it wasn’t actually a malfunction, but a deliberate thing.

This is from the days of full service gas stations (pre 1990s)
When gas station attendants did stuff like check your oil & tire pressure

Very interesting one. My dad was very good at A/C on cars. Back when gauges were the most important thing. He used those big (I guess they were 30lb) containers of Freon. He did a lot of A/C work. He even got a Freon recycling machine about a year or less before they banned R12. That pissed him off. As I type this on a PC over the internet, I marvel at the sheer complexity that the automobile has evolved into. Back when I was working on them they had already declared cars computers that just happened to have a gasoline engine attached. I remember reading in the '80s that the cars had more computing power than the Lunar Module and marveled at that. Don't get me wrong. I liked electronic ignition. Not having to mess with points was nice. Not having to deal with front drum brakes was also nice. But it's getting ridiculous. I'm just wondering when the A.I. assistant is going to glide up and offer to buy a cup of coffee for you.

You could always take the Short Circuit approach and disassemble the entire vehicle.

a willingness to jam your arm into a tiny space without complete assurance you’ll get it back

This is why I always got volunteered to be the one to put my arm places when helping my friends with their cars. Apparently if you have small, girly hands and arms, it's better than giant man hands that might get eaten by hungry cars. Still, I read that and laughed cause of the number of times I'd put my hand/arm places and be thinking "I better freaking get this back..."

Starting in the 2019 models, Ford requires a password and code to clear codes. Because of this I have determined that 34 years of doing this CRAP is enough!

I remember my old PT Cruiser.

I legit could not run the A/C at all during summer as it'd cause the car itself to overheat. Or overheat quicker.

I never did figure out what was causing that, but I do have my theory: If you listened close enough while the car was running you could hear a fan, I presume it was the radiator fan, clicking on for a little bit, the abruptly stop. On off on off on off, over and over and over again.

I think, though I'm not sure, is the radiator sensor was shot, or more likely damaged and thus caused it to become indecisive on being on or off. I say damaged as when I took it in for some body work for some reason I forget, someone doing the work ended up dropping a sanding block down into the engine and it got stuck in the fan casing. We only found it a year or two afterward but never actually investigated what the damage was from it.

I figure it literally sanded down some of the fan blades and other bits while being spun about really fuckin' fast.

And yet, despite that one quirk, that car was a damn good car to me. Even survived being hit by 5 different deer, if you'd believe.

I miss that purple piece of shit.

~Skeeter The Lurker

Ah, when the scanner data lies to you. My favorite. :ajbemused:
Also, how do you like the Autel scanner? I love mine. Anything else I use now just feels clunky or inferior.

The AC problems on the Chrysler vans where no fun. My parents had the AC go out while they where in the mountains in Colorado. They limped it back to Minnesota to my uncles garage, he is one of those country mechanics, and couldn't fully find the problem. So they drove it home and a few days later as I am out by the van that has not run since they got home and the fan is running. I just popped the hood and disconnected the fan and informed my dad. He misunderstood what I did and thought I disconnected the battery not the fan so several days later when he finally had the time to look at it the battery was dead. Still nothing beats the time a loose big rig tire took out my younger brothers van radiator as he was driving it in a construction zone.

These posts are fascinating, but for me, it's like visiting WebMd: I start seeing symptoms of problems where none exist yet. I have a 2018 Ford Escape, and it's given me no trouble whatsoever, but now I'm looking for problems in it after reading these posts.

5108842
Semi-related.

The old 1990 Chevy Lumina that I had for years (used to be grandma's car) had a fun A/C quirk: Under close/actual full throttle, the AC would just shut off. It wouldn't come back on until lifting off the throttle enough for it to kick into overdrive. xD

#error found #throw hashtags at it # someone's always lying about hashtag errors #throw more hashtags at the problem #hashtag error solved

FTL

5108896
A friend had an '08 Holden Commodore that he hated because it did the same thing. The ECM, by design, told the A/C to shut down at high load but over time the ECM's definition of 'high load' became anything beyond about 1/3rd throttle... thought it would be something else giving bad info to the ECM but it ended up being the actual ECM itself. After 2 years of substandard A/C we finally got around to fixing it... one new ECM later and the A/C again only shut off at near full throttle... just in time to have a dingbat in a cement truck make the Commodore a filling in a 5 car sandwich a fortnight later... but that's life, eh?

You know, I know next to nothing about cars. But I do know a lot about computers and the surrounding technologies. So it's actually kinda neat to see how universal troubleshooting logic is, and be able to follow that even not knowing much about what you're talking about.

Ah, Dodge Caravans. We had two of them while I was growing up, and I still prefer them over the standard four-seaters. (Though truthfully, if you can consider that Plymouth Voyagers weren't outwardly that much different, you could bump that number up to three. :)

Now kiss

LOL so funny!

Speaking of A/C... Y'know how I asked you if you had any ideas why my Sonata's A/C kept cutting out after a while, and you speculated that it might be freezing over? I think you were right. I say "were" because I'd had it set to draw outside air and then cool that. Probably not a great setting when it's 95 degrees and 80% humidity.

My A/C's probable reaction to the situation (dramatized):
giphygifs.s3.amazonaws.com/media/iVWO03WjTMbWU/giphy.gif

I switched it to recycle the cabin air, and it has functioned normally ever since.

Go me. :rainbowlaugh:

(Now I just need to figure out why my rear brake lights don't work.)

Admittedly, my skill at auto repairs is limited to duct tape and baling wire, but I have wished for a dead O2 sensor rigged to always give the 'right' answer after about the third one I replaced on one of our cars.

Ended with an eleven.

5108810
comparing modern computers to the Apollo Guidance Computer has always seemed a bit odd to me. though i suppose comparing to automotive electronics isn't as big a stretch as other comparisons.

the AGC, while rightly considered a marvel in its own right, was a custom-built embedded system integral to the command and lunar modules, meant to do ONE thing VERY well in conjunction with the entire spacecraft it was attached to, making comparisons to modern general-purpose PCs and smartphones somewhat misleading. people also tend to overlook an equally important computer on the Saturn V - the IMU on the third stage, responsible for launch and lunar injection.

if you (or anyone else) are interested, CuriousMarc on youtube has a whole series where he helps restore an AGC to working order.

>Dodge Caravan
>Air conditioning not working

pics.me.me/you-dont-say-memes-com-14014390.png

Once again, that was an adventure. (I would have said "an Odyssey, but that's the wrong model.)

5109335
And... did it do that one thing better than a modern smartphone could? If not, then it's only misleading in that it undersells the power differential.

5108802

Heh. My parents had two Grand Caravans over the years - a 1995 SE and a 1999 Sport. (still miss that electric blue with the too silly not to get spoiler)

I’ve had three (thus far)--a 2001, 2002, and 2007. The two newer ones are blue, and the oldest one is white.

Both of them eventually ran into a similar issue with the AC not running for what would seem to be inexplicable reasons. If I recall, changing that same sensor fixed the 95 van. On the 99, the issue was eventually traced to short outs in the board that controlled the climate control buttons, so the dealer had to basically replace the entire center stack, since it was all one assembly.

Thus far, the AC on my fleet has been reliable. Well, not so much the white one, but that didn’t work because I disabled it due to a mechanical failure, which was then followed by a deer strike . . . wasn’t worth doing five or six hundred dollars worth of repairs on a van that only cost $600, y’know?

One thing that was a known issue on the Caravans was that the HVAC module would get stupid for some reason (often after a low batter/jump start) and just needed to be rebooted. A lot of times, you could put it in self-test mode and that would fix it; other times, you could force a restart by disconnecting the battery and touching the cables together for about 30 seconds--that basically wipes the memory of every module on the vehicle [and can cause other problems if it’s been successfully compensating for another issue, but that’s another story].

My experience as a tech has been that the Caravans are generally quite reliable--not much seems to fail on them.

5108803

Uses -40 so it doesnt have to select a correction function, and its effectively a failsafe value, shutting the system down instead of burning the compressor out?

That’s just generally the lower spec that the temperatures are designed for. I don’t know the engineering reason behind that, other than once it gets that cold, there’s nothing to be gained by measuring colder temperatures, so there’s no need to have a temperature sensor with a wider range. Likewise, the upper end of most temperature sensors on a vehicle is above where the engine literally melts, which is good enough for that use.

There are some sensors that have a higher range, when they’re in the exhaust, for example [although typically exhaust temperatures are inferred rather than directly measured].

For the AC at least, the compressor would probably work at -40, and it might be used for the dehumidifying function, but it’s pointless to use AC for cooling at -40 on an automobile, since outside air is cooler than the AC system can produce. Obviously, industrial freezers of various types use different tech for a different result.

5108805

This is from the days of full service gas stations (pre 1990s)
When gas station attendants did stuff like check your oil & tire pressure

For me, it’s never in my life (at least, not in my memory)--Michigan’s been a largely self-serve state since at least the mid-80s. Heck, I once accidentally pulled into a full serve station somewhere in Indiana, and was very confused when the attendant ran over and stopped me from using the pump.

5108810

Very interesting one. My dad was very good at A/C on cars. Back when gauges were the most important thing.

Gauges are still somewhat important, when you have a system that’s working but not performing correctly--there’s a lot you can tell by what the pressures are doing. Although as IR cameras are getting cheaper, there’s a lot you can tell with them, as well, and of course you can measure more points in the system than just where the gauges attach.

He used those big (I guess they were 30lb) containers of Freon. He did a lot of A/C work. He even got a Freon recycling machine about a year or less before they banned R12. That pissed him off.

Yeah, I believe those are 30# containers. I think that’s pretty much the industry standard, at least in the US.

My boss has held on to a container of R12 just in case? I’m not sure what his thinking is, honestly. Even if we were going to service an older car with an R12 system--and if we could get the customer to pay the going value of the stuff--we don’t have a machine for it any more.

As I type this on a PC over the internet, I marvel at the sheer complexity that the automobile has evolved into. Back when I was working on them they had already declared cars computers that just happened to have a gasoline engine attached. I remember reading in the '80s that the cars had more computing power than the Lunar Module and marveled at that. Don't get me wrong. I liked electronic ignition. Not having to mess with points was nice. Not having to deal with front drum brakes was also nice. But it's getting ridiculous. I'm just wondering when the A.I. assistant is going to glide up and offer to buy a cup of coffee for you.

To my mind, since I came to the game after computerized engine controls were already a thing and had been for a while (I didn’t start until a few years after the OBD-II standard was established), it actually seems less complex than the older mechanical systems. Hell, on my 84 S-10, to control the spark timing, there were thermal delay valves, vacuum, advance, centrifugal advance, and obviously you also needed a timing light to set base timing . . . now, there’s a sensor that tells the computer where in its rotation the crankshaft is, and the computer can set the timing to whatever it wants.

Sure, there’s some stuff that’s probably not needed, but at the same time, there’s a lot of stuff that does little subtle things that helps the car make more power with less, and overall, reliability, safety, and fuel economy have been greatly increased since the advent of computerized engine controls. And honestly, while my blog tends to skew things towards the electronic failures side--because those are interesting*--the systems are generally pretty robust.
_______________________________________
*I could write one blog post, maybe two, about replacing brakes before y’all got bored of that topic.

5108812

You could always take the Short Circuit approach and disassemble the entire vehicle.

I’ve essentially done that with a S-10. Not a terrible interesting learning experience, actually, although maybe if I’d done it before I got into the field, it would have been more eye-opening.

5108813

This is why I always got volunteered to be the one to put my arm places when helping my friends with their cars. Apparently if you have small, girly hands and arms, it's better than giant man hands that might get eaten by hungry cars.

It totally is. We actually first had our smallest guy get his hand in there and feel around, but he didn’t have the ‘finger experience’ to unfasten a component by feel (something I should blog about at some point, honestly). I also once used an eight-year-old girl as a lockout tool--her arm could fit through the gap in the window and reach the unlock button.

Still, I read that and laughed cause of the number of times I'd put my hand/arm places and be thinking "I better freaking get this back..."

I legit one time got my arm stuck between and engine and the body while the manager was at lunch, and had to disassemble part of the belt drive system to get it back. Would not recommend.

5108826

Starting in the 2019 models, Ford requires a password and code to clear codes. Because of this I have determined that 34 years of doing this CRAP is enough!

And they have some codes that can’t be cleared (although the engine light will go out, but it will retain in memory that that code has been set). And some failures on Chryslers can only occur a certain number of times before the computer locks you out forever.

There are multiple reasons for that, including vehicle security, emissions requirements, and people breaking their vehicles by using badly-designed programmers, along with people swapping in components they really shouldn’t . . .

For better or worse, it is really changing the repair industry.

5108842

I think, though I'm not sure, is the radiator sensor was shot, or more likely damaged and thus caused it to become indecisive on being on or off. I say damaged as when I took it in for some body work for some reason I forget, someone doing the work ended up dropping a sanding block down into the engine and it got stuck in the fan casing. We only found it a year or two afterward but never actually investigated what the damage was from it.

I figure it literally sanded down some of the fan blades and other bits while being spun about really fuckin' fast.

A lot of times, there are two speeds on the fan, fast and slow, and the car wants to run low speed unless it really needs high speed. Failed relays, or failing relays, could cause the fan to not be reliable at both speeds, but it might be able to keep the engine cool at low speed as long as it didn’t have too much heat load. Other vehicles have multiple fans, and sometimes they run one for normal cooling, and the second if needed; once again, a single fan might make things work most of the time, but when there’s a high heat load, it just can’t pull enough air.

Usually, just the engine coolant sensor controls the primary fan, although in some vehicles the transmission temperature sensor can also trigger it. Then it’ll have another strategy for when the AC turns on, which is usually turn the second fan on if they’re run independently, and then it will likely use the worse of AC pressure or engine temperature to control high speed or low speed.

Damaged fan blades could certainly cause it to not be able to cool like it should, at at least on more modern vehicles, might cause the AC to turn off to reduce engine heat.

And yet, despite that one quirk, that car was a damn good car to me. Even survived being hit by 5 different deer, if you'd believe.

My white van survived at least five as well . . . don’t have an exact number for how many hits it had before I got it, although guessing by the body repairs, it had had at least one before I got it, and I hit two and got hit by two more when I owned it.

I miss that purple piece of shit.

I’ve also had a couple of cars that I miss, even though they were huge piles. :derpytongue2:

5108852

Ah, when the scanner data lies to you. My favorite. :ajbemused:

I know, right?

Also, how do you like the Autel scanner? I love mine. Anything else I use now just feels clunky or inferior.

Honestly, we wound up not buying it, despite my recommendations. There was some stuff I preferred on the Snap-On, but the Autel was a good price (I thought) and had some extra features the Snap-On didn’t.

5108866

The AC problems on the Chrysler vans where no fun. My parents had the AC go out while they where in the mountains in Colorado. They limped it back to Minnesota to my uncles garage, he is one of those country mechanics, and couldn't fully find the problem. So they drove it home and a few days later as I am out by the van that has not run since they got home and the fan is running. I just popped the hood and disconnected the fan and informed my dad. He misunderstood what I did and thought I disconnected the battery not the fan so several days later when he finally had the time to look at it the battery was dead.

Did you ever figure out why the fan was continuously running? A lot of vehicles will run the cooling fan for a short time after the engine is shut off, but obviously shouldn’t run it continuously. I’d have to assume that a relay shorted on, although it’s possible that a wire shorted or that the PCM failed internally in such a way that it could not control the fan at all.

Still nothing beats the time a loose big rig tire took out my younger brothers van radiator as he was driving it in a construction zone.

Those things can cause an enormous amount of damage . . . if all it did was take out the radiator, he got pretty lucky, honestly.

5108872

These posts are fascinating, but for me, it's like visiting WebMd: I start seeing symptoms of problems where none exist yet. I have a 2018 Ford Escape, and it's given me no trouble whatsoever, but now I'm looking for problems in it after reading these posts.

:rainbowlaugh:

The only weird electrical problem I’ve dealt with on a late-model Ford SUV (and I can’t remember if it was an Escape or an Edge) was a failure of the infotainment system which we were unable to diagnose with the tools we had. It turned out to be a software bug for which there was an update that the Ford dealer installed for the customer . . . apparently, if you tried to sync two different Apple devices, the system crashed and wouldn’t restart.

5108896

The old 1990 Chevy Lumina that I had for years (used to be grandma's car) had a fun A/C quirk: Under close/actual full throttle, the AC would just shut off. It wouldn't come back on until lifting off the throttle enough for it to kick into overdrive. xD

That was probably an intended strategy (assuming you mean A/C function only, not the entire HVAC system quit)--reduce extra engine load so it can put all its power to the wheels.

5108937
#you can never throw on too many #hashtags. :derpytongue2:
(I actually have a lot of fun with putting on a number of relevant ones and then a few that are just silly).

5108949

After 2 years of substandard A/C we finally got around to fixing it... one new ECM later and the A/C again only shut off at near full throttle... just in time to have a dingbat in a cement truck make the Commodore a filling in a 5 car sandwich a fortnight later... but that's life, eh?

That’s the worst. Like the time I just put new front fenders on my truck, and also fixed something else (can’t remember what, now), and while I was on a test drive, some guy ran a stop sign and totaled it.

5108991

You know, I know next to nothing about cars. But I do know a lot about computers and the surrounding technologies. So it's actually kinda neat to see how universal troubleshooting logic is, and be able to follow that even not knowing much about what you're talking about.

When you really get down to brass tacks, it’s probably exactly the same as troubleshooting computers. You want to know if it’s seeing the inputs, and you want to know if it’s controlling the outputs, and then from there investigate the root cause.

5108995

Ah, Dodge Caravans. We had two of them while I was growing up, and I still prefer them over the standard four-seaters.

They’re really great vehicles. The only downside is getting past the ‘soccer mom’ vibes of a minivan.

(Though truthfully, if you can consider that Plymouth Voyagers weren't outwardly that much different, you could bump that number up to three. :)

And if you want to bump it up to four, the VW Routan was a rebadged Grand Caravan.
upload.wikimedia.org/wikipedia/commons/f/f2/2009_Volkswagen_Routan_SE.jpg

5109129

Speaking of A/C... Y'know how I asked you if you had any ideas why my Sonata's A/C kept cutting out after a while, and you speculated that it might be freezing over? I think you were right. I say "were" because I'd had it set to draw outside air and then cool that. Probably not a great setting when it's 95 degrees and 80% humidity.

That’s very possible. A lot of times the owner’s manual will say how you should set the system for particular situations, and they might recommend using recirc for high heat/humidity . . . it would certainly make the system not have to work as hard.

My A/C's probable reaction to the situation (dramatized):

:rainbowlaugh:

(Now I just need to figure out why my rear brake lights don't work.)

Do none of them work? Does the cruise control work? Have you tried replacing the bulbs?

5109154

Admittedly, my skill at auto repairs is limited to duct tape and baling wire,

That can be a functional repair. My minivan’s still got one tailtight Gorrilla-taped in, ‘cause I haven’t cared enough to fix it right.

but I have wished for a dead O2 sensor rigged to always give the 'right' answer after about the third one I replaced on one of our cars.

The problem with that idea is that over time, a sensor that’s always showing a ‘good’ value even if it isn’t might wind up causing serious engine or exhaust system damage. One of our trainers tried that on a Dodge Caravan just to see what kind of effects he could make it have on fuel economy, and he wound up melting the catalytic converter in a couple hundred miles of driving.

5109483
I’ll be honest, of my three, it works on two of them, and the other one doesn’t work because I disabled it, and then hit a deer.

5109513

Once again, that was an adventure. (I would have said "an Odyssey, but that's the wrong model.)

:heart:
Also, speaking of Odysseys, if I ever have the chance to have the door pad off the sliding door on one of those again, I’ll take a picture, ‘cause it’s hellishly complex what’s going on in there.

5109335

the AGC, while rightly considered a marvel in its own right, was a custom-built embedded system integral to the command and lunar modules, meant to do ONE thing VERY well in conjunction with the entire spacecraft it was attached to, making comparisons to modern general-purpose PCs and smartphones somewhat misleading. people also tend to overlook an equally important computer on the Saturn V - the IMU on the third stage, responsible for launch and lunar injection.

I’ve often found that a particularly odd comparison, as well. PCs and smartphones are designed to do a bunch of different things decently well; wheras things like the AGC or the PCM on a car are designed to do one task very well, and not much else. The PCM in a car, for example, has pretty crappy processing power compared to an off-the-shelf laptop, but you can’t expect an off-the-shelf laptop to work if directly wired to eight 40kV ignition coils, nor function in an environment which might range from -40F to 300F, nor cope with all the vibrations and dust a PCM might have to deal with over its lifetime.

While I’m not much of an electronic geek, I do have a soft spot for machines that are designed for one purpose and which carry out that one purpose flawlessly.

5111272

Nope they ended up junking it not long after. It had 250000+ miles on it so they didn’t want to spend the money on fixing it.

As for my brothers it was inches from getting the engine and clipped the top of the roof after it hit the radiator. He knows how lucky he was. However they never found out what truck it came off of.

5111280
Sadly, we've never had a Routan. 😞 After most of us kids moved out (eventually permanently), my parents made the switch to smaller cars. My dad's owned a Honda Civic with a hybrid engine since... I want to say 2004 or thereabouts, while my mom prefers the Toyota Corolla Matrix that she got in '06.

5111255
Looking at it, the idea started in 1964, got traction after the gas shortage in 1973 & 74, & took off after they invented “pay at the pump” in the mid 1980s. But you could still get full service until, oh, the mid 90s (it cost more but handicapped, for instance, would pay for it)

Now, self service is illegal in Oregon & New Jersey + some towns here & there. Otherwise, the cost difference makes it pretty much all self serve

Old folk’s rambling
I’m in Phoenix, Az. Back in the 90s I was working at a convenience store/gas station & someone from Oregon pulled the nozzle out of the car & hosed me down with gas “Oh, I wanted to see if it was pumping” (Back then, they didn’t have an automatic cut off for things like that)

My mom worked in the first self serve in our hometown. She wasn’t supposed to leave the booth. She said she’d see people put it in the radiator. She also said that people would bitch about the cost of cigarettes & tell her “I’ll quit smoking when the price of cigarettes hits $1 a pack” She’d laugh in ttheir face

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