Automotive Air Conditioning Information Forum (Archives)

arnea on Mon June 25, 2012 9:28 AM

Year: 1997
Make: Chev
Model: Suburban
Engine Size: 5.7
Refrigerant Type: R134a
Ambient Temp: 86
Pressure Low: 36
Pressure High: 360
Country of Origin: United States

The A/C system has worked OK as long as the outside temps are below 85 degrees. Lately I've noticed that sometimes when I start the A/C system that air will be hot at the beginning and then begin to cool after 5 minustes or so. I mangaed to pull over when this happened recently and found the clutch disengaged and then suddenly engage. I measured the clutch gap to be .016. Are these models prone to have relay failures??? I have evacuated the system several times over the last few years and add 64 oz of R134a for a dual system. It does seem to cool better on the road than in stop and go traffic. The condensor is clean. Does it need a pusher fan???? Also, what is the correct orifice tube??White..or white and yellow???? thanks Arne

GM Tech on Mon June 25, 2012 10:23 AM

Sounds like a bum fan clutch and you have high pressure cut-outs---how much air is crossing the condenser at idle? spray it with water see if it cools better- and check the air flow behind the cooling fan...

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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......

arnea on Mon June 25, 2012 10:56 AM

the fan Clutch has been replaced.


I have cleaned the condenser and the faster you drive the cooler it gets up to 85 degrees. Are the pressures OK???

GM Tech on Mon June 25, 2012 12:46 PM

360 head pressure is way too high about 100 psi too high-- did you pull a vacuum prior to charging? could be air in the system...

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

arnea on Mon June 25, 2012 1:39 PM

I did pull a vacuum for about 75 minutes and added using an electronic scale 64 ozs. Could the system have too much oil????

GM Tech on Mon June 25, 2012 2:13 PM

Mist water on condenser from a garden hose and report back discharge pressure...

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

arnea on Wed June 27, 2012 11:24 AM

Wife took the truck to visit the daughter for a week. Will mist condenser next week. Question: With an ambient of 86 degrees and a low side of 36 and a high side of 360...would that indicate an overcharge of oil or possibly the wrong orifice sized tube???

GM Tech on Wed June 27, 2012 12:26 PM

Indicates an air flow over condenser issue-- or a partially plugged orifice... oil doesn't cause high head unless it is completely full of oil....saw a C/K truck once with 48 ounces of oil in 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......

arnea on Wed June 27, 2012 1:45 PM

It certainly doesn't have 48 oz of oil. I had flushed the system several years ago when the compressor failed. I did install an aftermarket condenser but have an OEM GM ready to install when I need to. I am not sure as to the OT. It is either going to be yellow or white. If it had the white OT...would that cause r high pressures nd..Does the higher pressure prevent the system from cooling when the temps go above 90 degrees????