QuestionDavid,
The 100 psi on the low side was with the system running. I bypassed the pressure switch on the accumulator and let it run for a few minutes. While the pressure went down as the system ran, it stopped dropping at about 100 psi.
Since I posted, I opened the system up. Neither the orifice tube nor the expansion valve (in the rear A/C unit) show any signs of debris and the tubing into and out of the compressor looks clean as well.
I'm suspecting a failing (or failed) compressor especially since it's making a fairly loud rattling noise that is not, as I recall, normal for this unit.
I'm planning on replacing the compressor, orifice tube, rear expansion valve, and accumulator and then have the system evacuated and recharged with R134a.
Hopefully that will take care of this.
One more question. How much, and where is the PAG lubricant added? My Chilton book says in one place to add it to the accumulator but in another place says to add it to the commpressor. Both places say to add an amount equal to what's currently in the accumulator or compressor. But I'm not finding anything in either of these other than just enough to coat the inside.
What about R134a with lubricant added already? Is that sufficient by itself? The system capacity says 2 lb. 8 oz. of refrigerant. If the cans have lube already added in the right proportion will that take care of the lubricant needs?
Thanks...
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Followup To
Question -
I have 99 Chevy Tahoe with 5.7L V8 and about 105K miles. A/C has never been worked on and has worked fine until recently.
Now the compressor doesn't turn on most of the time. I bypassed the pressure switch on the accumulator and the compressor runs and the air blows cold. Thinking that the R134 might be low I purchased a refill kit with a pressure gauge. But the gauge reads 100 psi on the low side which is probably why the pressure switch is keeping the system off.
Not sure why the low side pressure would be high, there is no way this should be overfilled since it's never been filled at all. I released some of the R134 until the low side pressure was down to where it should be and the system ran. It was ok for a few days but now it's doing the same thing again.
There is some noise coming from the compressor when it's running but not anything that I'd consider out of the ordinary. My 98 pickup has the same compressor and it sounds similar although not quite as loud.
Wondering, what might be wrong here? Bad compressor?? Could that cause the low-side pressure to be too high? Since this is a fairly expensive replacement part I don't want to just slap a new one on in the hopes that it might solve the problem.
Answer -
90 TO 100PSI WITH A/C OFF IS NORMAL.I NEED TO KNOW THE PSI WHILE RUNNING.LOW-SIDE IS 20-30PSI AND HIGH-SIDE-180-210PSI. IS NORMAL. GM HAS PROBLEMS WITH THAT SWITCH AND I WOULD RECOMMEND REPLACING IT AFTER YOU FIND HOW THE A/C IS PERFORMING.
GOOD LUCK,DAVIDT
AnswerHELLO JOE, WELL THIS IS WHAT I WOULD DO. REPLACE COMPRESSOR,ACCUMULATOR,ORIFICE TUBE. FLUSH THE TOTAL SYSTEM.
YOU LOST THE PUMPING ABILITY OF COMPRESSOR.OIL CAPACITY 6 TO 8OZ. PUT 2OZ IN ACCUMULATOR AND THE BALANCE IN COMPRESSOR.
CLOSE UP THE SYSTEM AND PULL VACCUM FOR 1HR. AFTER YOU DROP IN FREON,ROTATE THE COMPRESSOR HUB ABOUT 10 TIMES AND THEN START THE TRUCK.THE REASON FOR DOING THAT IS TO REMOVE ANY OIL FROM THE CYLINDERS SO IT DOESN`T LIQUID SLUG THE COMPRESSOR. IF YOU CAN,BUY A NEW DELCO COMPRESSOR NOT A REBUILT.POOR QUALITY.
GOOD LUCK, DAVIDT
