Automotive Air Conditioning Information Forum (Archives)

rojeho on Sun July 12, 2015 9:59 AM

Year: 2001
Make: Chevrolet
Model: Suburban LS1500
Engine Size: 5.3
Refrigerant Type: R134a
Ambient Temp: 85
Pressure Low: 95
Pressure High: 95
Country of Origin: United States

I had a catastrophic event that now continues to build. I need help!

Vehicle is a one owner, 166k miles, AC system not charged in the 7 years I've been in its life. I replaced a mag clutch a couple of years ago when the AC would randomly stop blowing for variable periods of time before starting to function as normal again all on its own.

Driving in traffic, AC blowing cold and all is well. At a stop light there is a loud shriek. At first I think bearing but it's not quite the same sound. It only lasted about three seconds and then stopped. As soon as it stopped the AC started blowing warm at the same fan speed. My wife thinks that the noise was very close, like under the dash.

I put the gauges on it this morning. Even pressures on both side, approx. 95/95. Magnetic clutch appears to be turning. When I took the gauges off the high side port continued to hiss. I couldn't see a Schrader valve in the port and don't recall if I could see it before I connected the hose. Put the fitting back on, opened and closed a couple of times but no change. I stuck a small screwdriver into the high port to see if the valve was stuck down, and, well, let's just say I let the smoke out in a forceful way. Got a good spray of compressor oil when this happened. I unscrewed the high side connector from the gauge hose, and this stopped the venting.

I need some direction at this point. First I need to figure out what happened with the high pressure fitting and how to get that sealed again, and then troubleshoot what failed.

Thank you!

1wheeler1 on Sun July 12, 2015 11:29 AM

Not sure on the original noise/failure but on my 1998 suburban and a lot of vehicles the high side is a rubber ball valve instead of a Schrader. From what I understand over time the rubber portion gets the sealing edge molded into it and when you connect/disconnect the ball position can change and re-won't seal. They are unscrewed with a special socket that fits the six sided shape around the ridge that the gauge connector snaps onto not the normal wrench area at the bottom of the fitting. Usually you can get it off with a crescent wrench instead of the special socket. On amazon the AC Delco one is about $7.

I'm new at this working on my own vehicle but pretty sure you need to have it recovered/empty before you can change that valve.

First thing I would do is unplug the compressor clutch so it's no longer pumping in case you had a major compressor failure so it doesn't contaminate the rest of the system and then go get it recovered/empty so you can change that valve and check the condition of the orifice.

Here's my valve on Amazon
http://www.amazon.com/ACDelco-15-31708-Professional-Conditioning-Charging/dp/B001O83VMG/ref=sr_1_1?s=automotive&ie=UTF8&qid=1436713438&sr=1-1&keywords=15-31708


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“I’m so thankful I had a childhood before technology took over”

GM Tech on Sun July 12, 2015 11:38 AM

The original compressor clutch just needed a shim removed-very common failure mode when air gap gets too wide.- no new clutch needed.

Check belt and/or tensioner on your low mount compressor- the belt may not even be on- seen this before.

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The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

rojeho on Sun July 12, 2015 6:58 PM

Thanks GM-Tech. You helped me on the first go around with the intermittent, but when I took off the clutch there was no shim. The new one was so cheap that's why I replaced it, and the system was flawless for 2 or 3 years.

The belt is on and looks fine. That was my first guess and watched gauges but everything was normal, just warm air. This morning when I started the truck to check pressure the belt looked good and it starts with no squeaks or other oddities. I drove it for 40 miles last night after the screech.

I need to fix what I broke on the high side valve but then I am still back to the original. What would cause a three second shriek that sounded close enough to be under the dash (or maybe not, but it sounded really close) that as soon as it got quiet the AC was no longer blowing cold air?

I expected to find an empty system and visions of a hole in the evap and taking the dash apart, so I was surprised to see 95/95 on the gauges before I made the situation worse.

rojeho on Mon July 13, 2015 8:00 AM

Actually I went back to my records to check. I did take out the shim from the original, and it worked for about two months before symptoms reappeared. That's why I changed the clutch.

Sounding like I have a dead compressor at this point? Guessing I should replace the condenser and orifice tube and receiver drier? Anything else? Anything related to the rear AC that I should also replace?

This is a great forum. I really appreciate the help here.