Public Service Announcement - Aveo cooling system electrical issues (SOLVED!)

[MichiganMadMan]

Hello fellow Aveo owners,

I've noticed a few things on the Aveo I bought and wanted to broadcast these to other owners so they don't experience the same issues.

Backstory: I changed jobs recently and am working remotely from a different state. This requires some long drives and I wanted the smallest car I could fit in. I found a beat up, neglected 2009 Aveo5 with a manual transmission last summer to fill this need. It had a multitude of issues, but I'll be focusing on the cooling and A/C system ones here.

When I bought it, the A/C wasn't working. The compressor would engage, but warm air would blow out of the vents and the lines were not getting cool. The pressures were OK when the system was at ambient (engine off), but the high side would not climb when the compressor was engaged.
Looking around on this board, this story is repeated endless times.

Two possibilities: The compressor or the expansion valve have packed up. I replaced the expansion valve (cheaper and easier), nothing. I ended up replacing the compressor AND the condenser, because it has an integral filter that can't be replaced. When I fired it up after replacing all these components, the fan DIDN'T turn on. It also would never engage at high speed for reasons I don't know. This means the A/C has no flow over the condenser. This only persisted for a few seconds on mine, so there was no damage. I jumped the low speed relay and the A/C works fine.

Here is what I think happens on these cars:
The low speed fan craps out due to electrical issues, the system doesn't switch to high speed for whatever reason, and the refrigerant boils in the system and destroys the compressor.

Cooling fan issues I have found on mine: The low speed fan relay was kaput when I got the car. I had to find a replacement at the auto parts store based on the function of the relay. They didn't list it specifically for my car. Recently, the low speed resistor has bit the dust, again disabling the low speed fan.

Great. So what can we do about it?

Options: Find a wire that is hot when the key is on, install a relay and jump to the high speed fan output. This would turn the fan on high any time the key is on. Since I don't live in Phoenix, this seemed a bit extreme to me. You could do the same thing with the low speed fan, so it would be on any time the key is on. Again, I live where it gets cold in the winter and I don't want to have a fan on when it's below 0.

Plan for my car: I am going to wire up a switch inside the cab of the car so I can over ride the engine controls and engage the fan. Scratch that, two switches. If you have only one, you either have high speed all the time (with the corresponding electrical load and noise) or if you do only low speed you run the risk of having that resistor check out and stop your fan (like what happened to me recently). I'll be turning on the low speed fan whenever I have the A/C engaged, and use the high speed as a backup in case that resistor buys the farm again or I'm climbing a big hill, etc.

Look for a write up soon.

In the mean time, keep an eye on that cooling fan. It seems like it wants to quit working frequently.

[Daox]

MichiganMadMan, thanks for the insight into the Aveo A/C system. I look forward to the write up and hearing how it works out for you.

[MichiganMadMan]

Snapshot of the stock cooling fan wiring:


Over ride with low and high speed fan over ride switches:


I'll be taking pictures of my install as I go along as a reference for anyone who wants to do the same.

[avguy]

You've done a nice bit of diagnosis and analysis, but there's one thing I'm not understanding. Why not continue along the path you've already traveled so far on, and fix the actual fan issue, instead of resorting to manual switches?

Diagnosing the actual issue with the fan shouldn't be too much more effort. The usual suspects would be a fan motor issue, or some type of binding or other restriction of the fan, causing all of the related issues of high draw. Not trying to be critical of what you're doing, just wondering why you're avoiding the more typical approach to repairing an issue like this (which I'd expect to either be repairing the fan if possible, or hanging on a new fan assembly, if not).

[MichiganMadMan]

From what I can tell, the fan is the only part of the system that is working properly.
It spins freely by hand, spools up fine when battery voltage is applied directly, and the resistance is within the specifications in my repair manual. If the high speed circuit blew a fuse (the 30 amp circuit where the fan was directly connected to the battery), I'd suspect an issue with the fan itself.

As for what caused the initial low speed relay to quit, I don't know. I've been less than impressed with the electrical system in general on this car. The fuse blowing on the low speed side was due to the failure of the inline resistor. It likely has a crack internally and overheated. When these types of resistors are overheated, they momentarily have nearly a direct connection (the resistance drops for a second) right before they die. This is what I suspect happened to mine and caused the low speed 20 amp fuse to blow.

My conjecture is that the fan is fine on these cars but the wiring, particularly on the low speed side, is the weak point.

[avguy]

OK, your car, your choice. Hope your project works out well.

And thanks for letting others know what you found out.

[MichiganMadMan]

Update on resistor:
I knew the fan resistor had an issue because there was voltage when expected on one side, and nothing on the other. The fan worked (on high) when I jumped around the resistor.
Well, it turned out the resistor was cracked in several places and had infinite resistance. The part number I found was 94812213, purchased on Amazon.com. The corrosion on the electrical attachment screws was epic, so I had to cut the wires and install new terminals. Then I re-installed the resistor and the low speed fan selection is working again.

Just a note: This failure is not detectable by the ECM, and no codes were current or pending. Furthermore, the corrosion was nasty and I couldn't get the screws to budge, meaning a roadside repair is generally not possible. For this reason, if I were going to install only one bypass, it would be on the high speed side, where there isn't this problematic resistor involved.

[MetroMPG]

Thanks for the update, MichiganMadMan. Glad you solved the problem.

[AndrewButler05]

That's how mine was when I replaced it. I made new ends for the screw terminals, and put heat shrink over them to help protect them from roadspray. I guess when I noticed mine was disintegrating and replaced it, I dodged a bullet. Also ordered mine from Amazon.

Somehow mine was still working, but chunks of it were missing. lol

[MichiganMadMan]

The weather was finally a little better so I was able to make some progress on the manual over ride switches and wiring. It's a bit fiddly, but I like the idea of being able to intervene directly if the resistor decides to die on me again and take out the low speed fan.

I ended up intercepting both the fan LOW and HI circuit as it exited the fuse box under the hood. I got power from the input feed to the fuse box, I bought the pre-made fuse holders and offset them a bit.