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intermittent AC cooling - 2001 Suburban

rojeho on Sun June 10, 2012 11:47 PM User is offline

Year: 2001
Make: Chevrolet
Model: Suburban 1500
Engine Size: 5.3
Refrigerant Type: R134a

Problem started last year and may be getting worse. At random times (idle or while driving) the AC will cut off. Fan stays running but it gets hot and humid. Whenever it decides, it will turn back on. I've tried changing all of the settings and I can't make it come back on until it's ready. Sometimes it's 30 seconds, sometimes minutes. When it works, which is most of the time, it cools just fine. Of course it won't do this in the driveway so I can't check for the compressor running, pressures, etc.

Hopefully this is a relatively common GM thing that someone's heard before.

buickwagon on Mon June 11, 2012 12:54 AM User is offline

What RPM in the driveway? Is there a high-pressure cut-off in that system?

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I've saved hundreds on service by spending thousands on tools.

GM Tech on Mon June 11, 2012 6:17 AM User is offline

Typical of wide air gap issue on compressor clutch- once warmed up, the magnetic field is not strong enough to pull in the clutch driver over a widened (worn) air gap. Those low mount Sanden compressors can easily be accessed to pull off the clutch driver and remove a shim to lessen the air gap once you remove the splash guard.

Test by recognizing when a/c is not cooling when it should- then pull over and tap on front of compressor clutch with a blunt object... if clutch engages, then you know for sure yours is an air gap isssue.

I've done about a dozen 5.3L engine compressors this manner- all were successful.

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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 Tue June 12, 2012 10:11 AM User is offline

Quote
Originally posted by: GM Tech
Typical of wide air gap issue on compressor clutch- once warmed up, the magnetic field is not strong enough to pull in the clutch driver over a widened (worn) air gap. Those low mount Sanden compressors can easily be accessed to pull off the clutch driver and remove a shim to lessen the air gap once you remove the splash guard.





Thanks GM Tech. I will look at it this weekend and come up with a strategy to be able to whack the compressor next time it happens to see if I can isolate it to this problem, but what you describe is consistent with its random behavior. Do you know if there is a writeup or something to describe pulling off the clutch driver and removing a shim? I'll be brave but would like to know what I'm getting into.


GM Tech on Tue June 12, 2012 5:41 PM User is offline

Official "write-up to remove a shim"

1. Remove bolt in center of front of compressor

2. Wiggle clutch driver off of spline- be sure to gently remove it so as not to drop out any shim(s).

3. Remove the thickest shim and discard.

4 Put clutch driver back on splines.

5. Insert bolt and tighten.

-------------------------
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 Tue June 12, 2012 10:00 PM User is offline

OK, I feel stupid now but it's hard to do sitting in a hotel room not near the vehicle to look at it. Thanks for being kind.

rojeho on Wed July 18, 2012 12:51 AM User is offline

System finally went into fail mode. The periods when the AC kicked itself off became longer. Compressor not running when this happened. Finally it got to the point where there was no cooling and it never restarted. I removed the center bolt, but then couldn't get the magnetic clutch off. I could wedge a screwdriver in but it wouldn't move out on the shaft to come off. Finally gave up and put the bolt back in. It did the trick and the compressor started on the first try. Any tricks to get a 12 year old, 140k mile clutch to come off so that I can remove a shim?

In the picture below you can see a shiny spot on the compressor where I was trying to use the screwdriver.

http://i1107.photobucket.com/albums/h390/rojeho/Misc%20pictures/suburbanacclutch.jpg

GM Tech on Wed July 18, 2012 5:33 AM User is offline

up down left right wiggle wiggle wiggle- two screwdrivers back and forth is how I do it...

-------------------------
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......

Cussboy on Wed July 18, 2012 10:41 AM User is offline

Quote
Originally posted by: GM Tech
up down left right wiggle wiggle wiggle- two screwdrivers back and forth is how I do it...


GM Tech - you must have a proper tool for this, right?

rojeho on Thu July 19, 2012 12:37 AM User is offline

Thanks, just wanted to make sure before I did that.

rojeho on Mon August 20, 2012 10:51 PM User is offline

Took the clutch off and only one washer/shim came off with it. I removed that one and put the clutch back on. Worked fine for a month and I've now had two times when it's stopped cooling again. Were there more shims that just didn't come out that I should coax out? Or is this just a sign that I'm needing a new compressor?

GM Tech on Tue August 21, 2012 4:29 PM User is offline

Only you can decide if there are more shims--they come with anywhere from 1 to 3- depending on dimensional stack-up---grind some off end of driver or shaft if you are out of shims..

-------------------------
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......

AutoCool on Tue August 21, 2012 6:23 PM User is offline

There may be more shims still inside the hub you removed. Maybe the clutch gap has been adjusted before = no shims left to remove but take a good look inside the hub again and see if there are any shims left. If that's the case, you're either looking at a new compressor or a new clutch hub at the very least.

Did you measure the clutch gap with a feeler gauge?

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