2009 Aveo 5 A/C not cooling.

[MichiganMadMan]

Hey forum members,

I recently bought a 2009 Aveo 5 that had non-functioning A/C system.

Here is what I found:
The A/C compressor would engage (and stay engaged), but none of the pipes were cold. Ok, so time to check the A/C charge to make sure.

I hooked up my Harbor Freight A/C gauges and found that low side was high and the high side was.....low. Basically, there wasn't enough of a pressure difference between the high side and low side to create any meaningful cooling.

So it's either:
1. A bad expansion valve, it's not closing properly and restricting the high side.
2. The compressor has had it and is not pumping well enough to create the pressure that is needed.

Question for the forum members: Are either the expansion valves or compressors known problems with Aveo's? I don't want to do the job twice, but I also don't want to replace parts that don't need it.

[petrified.rabbit]

I would say before replacing anything, but you say there was not much difference between the two pressures?

Maybe there wasn't enough refrigerant to make the system work, but enough to keep it from shutting off?

From my experience, when initially starting the system, if the pressure climbed throughout the system, it is the typically the expansion valve. If it never built any pressure, it is usually the compressor. Im not sure what you can see.

I would try adding a few oz's. 3-4 and see if it changes anything. If it does, add some more until you get the pressures, cold air amount you are looking for. If it does not. You can get a used compressor for @ $50. (there is a yard in roseville mi Highway Auto Parts MIDW) that lists one for $40. Or waste time with replacing the relief and controls valves, I would buy a new valve though, for about $20 aftermarket. So opening the system, replacing both items for @ $75, repaired with $25 coolant, $100 repair.

[MichiganMadMan]

I would say before replacing anything, but you say there was not much difference between the two pressures?

Maybe there wasn't enough refrigerant to make the system work, but enough to keep it from shutting off?

From my experience, when initially starting the system, if the pressure climbed throughout the system, it is the typically the expansion valve. If it never built any pressure, it is usually the compressor. Im not sure what you can see.

At rest, the whole system is around 150 PSI. When the compressor engages, the high side jumps up a little (around 200) and the low side goes down a little to 100 PSI, then they settle around 175 PSI on the high side and 115 PSI on the low and stay there.

With the whole thing being at 150 just sitting there, I doubt it needs more refrigerant. I added a small can of UV tracer dye when I first started (before I remembered I had my Harbor Freight gauges in the basement) because I thought I was looking for a leak. It took a while to empty that can. To me this is pointing to a system that has plenty of refrigerant, just not enough pressure difference.

[petrified.rabbit]

the fact that it went up is a sign the compressor works. Sitting idle at 150 on both sides is high, too much pressure. If its @ 100 degrees outside, it would only read like 130psi. (Ill take into account those are harbor freight gauges, and that it might be overcharged slightly).

If the high side goes up, and the low side goes down, it "sounds" like the compressor is working. It sounds more like the expansion valve is open.. but it could also be the control valve on the compressor.

Reading the gauges will often tell what is wrong, I am not going to suggest anything but reading:

Troubleshooting with Gauges FAQ

R134a Pressure Gauge Readings

[MichiganMadMan]

So...the compressor is kaput. Installed the new expansion valve, pulled the system down with a vacuum pump and re-filled to a more normal level but the performance is as before.

Looks like I'm swapping out the compressor this weekend....

Thanks for the input and references.

[MichiganMadMan]

So update on this:
I replaced the compressor and found out some fun stuff. Normally you have a filter/dryer in the system that needs to be replaced when you install a new compressor. On a 2008 and older, this is a soda-bottle sized component on the driver side of the condenser. HOWEVER on a 2009, this is thoughtfully integrated into the condenser itself. This meant I had to either use the old crummy one, or replace the entire condenser with a new one.
Since I don't want to do this job again, I decided to replace the condenser also. Off to the auto parts store (again).

I fired it back up and started charging the A/C system. It was then I realized that the compressor was engaged but the cooling fan wasn't on. I shut off the A/C and started digging around. The ECM controls which fan speed is selected, so I pulled the low speed fan relay under the hood and checked the wires. There was 12 volts across the control circuit and the fan would turn on when I bridged the switched side of the relay. This meant that the low speed fan relay was kaput.

My guess was that this failure was the first thing that went wrong. The cooling fan must come on with the A/C to keep the condenser cool, but that wasn't happening with the relay being busted. This means that the A/C temperature was off the charts on the high end and cooked the compressor.

I was lucky in that my local O'Reilly auto parts was able to match me up with a relay that worked. I'm back on the road with ice cold A/C.

What a job though!