The AC in my Cadillac began not cooling at an idle and I figured it needed a shot of Freon. It did this for 2 days and the wouldn't work at all.
I bought a can of the proper Freon and it came with a gauge on the can. When I hooked it up to the low side (it would only fit on the low side so I know I had it hooked up right) it showed 90ish pounds instead of the fully charged 50ish with the compressor running.
I put a couple of squirts in and predictably the pressure rose and no cooling. I scratched my head and bled it a little ånd still no cooling so I decided the gauge must be wrong and added Freon, but still no cooling.
What are the things I should check? I'm presuming something is broken rather it just being a freon issue.
Are the lines between the compressor and the firewall getting hot and cold? If you're getting cold going into the cabin, then your issue is likely in the heaterbox. Blend door or something not switching properly.
Low side pressure that high when it was working immediately prior suggests mechanical failure of some nature. I'd put money on the compressor's retirement, perhaps a broken valve or failed variable displacement component (based on WAG that it's a late-model of some kind). You didn't mention year/model, but it's also possible the TXV failed if equipped.
Laserface's suggestion is also a good idea and super easy. Check to make sure your electric cooling fan is working normally as well.
Is the compressor making any unusual noises? Do you have a friend with gauges?
90 psi LS with the compressor running? Isn't that....really high? what are your HS pressures?
one of my older GM vehicles did this suddenly a while back, it ended up being the blend door actuator in the dash had failed so it just wasn't switching over to full cold.
Need to know the high side pressure, but it sounds way overcharged. Or the compressor is off.
If you have been topping off willy nilly, really the first step is a complete evacuate and recharge. You cannot really tell state of charge by pressure until it is REALLY low. Low side will always be in the 30-35psi range because any lower than that and the evaporator can ice over.
Sounds to me like the compressor isn't running.
agree with Toyman!. find the AC relay and give it a tap with a screwdriver when the system is ON, and see if that makes the compressor kick on. there are cutoff switches on low-pressure and high-pressure plumbing, as well as a relay for compressor. On my 2010 Sube, the compressor relay also powered the secondary radiator cooling fan. My relay was failing, which caused intermittent "no compressor", but it was the "no secondary fan" which led me to the relay as the culprit. IDK if GM system would be same. FWIW, on the Sube, with system ON and running the low-side pressure was in the 35 psi range and high-side was ballpark 250 psi IIRC. with system OFF, pressures balanced around 100 psi.
Unless it is pretty old at this point, the fan is controlled by the engine's computer based on high side pressure, not just if the compressor is running or not. Vehicle speed may also factor in.
To the best of my knowledge the AC has never had freon added. I know I've never added it or even needed to service the AC at all.
The compressor is kicking on. I'll check the lines for temp in the morning.
I don't think I have a way to check the high side, although I do have home AC gauges. I'll see if they have the same connector in the a.m. as well.
In reply to carguy123 :
You need to be able to measure the high side pressure.
What are your pressures with the AC off.
If the compressor is running and not making pressure, it has broken internally. Probably a valve if it isn't growling or rattling.
AngryCorvair (Forum Supporter) said:
agree with Toyman!. find the AC relay and give it a tap with a screwdriver when the system is ON, and see if that makes the compressor kick on. there are cutoff switches on low-pressure and high-pressure plumbing, as well as a relay for compressor. On my 2010 Sube, the compressor relay also powered the secondary radiator cooling fan. My relay was failing, which caused intermittent "no compressor", but it was the "no secondary fan" which led me to the relay as the culprit. IDK if GM system would be same. FWIW, on the Sube, with system ON and running the low-side pressure was in the 35 psi range and high-side was ballpark 250 psi IIRC. with system OFF, pressures balanced around 100 psi.
GM is generally similar pressure to this.
Since he said the low side was 90 (!) psi, I would definitely not jump the AC relay. That would bypass the overpressure switch and could pretty easily blow something up with it overcharged that much. When I bought one of my trucks, the system was overcharged pretty badly like this. It would trip the 500 psi overpressure switch within 15-30 seconds even if it was running just a hair above idle.
I ended up taking this to a shop since I realized that regardless of what I was going to have to evacuate the system and recharge and I didn't have the equipment for that.
Turns out it is a stuck expansion valve which on this car requires removal of the dash as it is on the coil inside the car and it's $1,300 PLUS it is supposed to take 2-3 weeks to get the part.
How do you like them apples!?!?!?!
Picked the car up and guess what? The AC worked so apparently the expansion valve is sticking and not completely gone. I just can't see spending $1,300 on a 2013 car and if it requires removing the dash I can't envision me having the time or inclination to tackle that. I only like to do fun jobs any more
