benjisuburban

Hey all,

I got the phone call from the girl that went like this: "Ummm, my ac isn't blowing cold air. We just had it recharged last year, what the heck?" Its a 2016 4wd LTZ 5.3 with dual air.

Well, its just starting to get warm up here in the PNW so its the first time AC has been used for about 7 months. I verified that it was indeed blowing air, so blower motor is good. However, she was correct, it wasn't blowing cold air. Front and rear vents were the same temperature and I confirmed everything was adjusted properly for temperature and ac button on etc.

I got my r134a sniffer out and started checking the condenser and lines and connections and nothing set it off so I didn't think there was a leak.
Next I hooked up my gauges and monitored them. Ambient temp was around 72 degrees outside and my pressures read as follows: Low side would climb to approximately 30-32 and then drop down to 20ish, then climb back to 30-32 again. I assumed this was due to the compressor kicking off and on. High side would climb to almost 145 and then drop down again about 15 degrees before climbing back up.

According to my AC pressure chart, that is a tiny bit low. Which points to the refrigerant being low. But, I was thinking it should still at least be blowing cooler air then ambient shouldn't it?

Secondly, is the ac compressor different than "other" compressors? I drive a subaru. The clutch system is obvious on that and I can tell when its turning off and on by looking at it while its running. On the 'burb, it doesn't look the same and I couldn't see any noticeable difference so I don't know if its kicking on or off, it just looks like it is spinning the whole time.

Any help will be greatly appreciated! My babies and their mama will be happy!!

Cusser

Disclaimer: I've never even looked at a GM newer than 2014.

Here's what I would do to check whether the compressor is engaging. Put a chalk line or white paint line on the compressor drive plate, see photo. When the AC is on and engine running, the drive plate with the white line should turn at same speed as the pulley and belt.




Your pressure numbers indicate that the compressor is engaging at least sometimes (high side would climb to almost 145) but one needs to find the leak before adding refrigerant. But that assumes that your AC compressor clutch is working when it should.

benjisuburban

Thanks for the advice. I’ll be taking home our ac machine from work this week sometime and pulling refrigerant to see what it has in it. I’ll also get it jacked up so I can trace the lines to the rear too.

Cusser

Wow - that's a great advantage, you'll be able to weigh the refrigerant charge and compare to the system's capacity.

Common for the service valves and caps (the real seal) to leak refrigerant (on all vehicles).