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Posted: 7/18/2010 7:01:10 PM EDT
got the bad news a couple of weeks ago...a/c compressor is shot in the wifes burb.
2001 chevy suburban with the 5.3l engine and rear air
so today got out and changed it out along with a  drier and oriface tube. took every precaution against contaminating the system kept the lines covered to keep dirt out, filled the comp away from the car and replaced the temp port cover to keep out dirt, did the same with the drier. flushed system as best as I could.

did everything according to the book 2oz pag oil in comp and 2oz oil in drier, rotated the comp by hand 10 revolutions before installation.
vaccumed system and it held vacuum for 10+- minutes @28-29 inches.

added r134a and here is the issue:
I put approximatley 3 12oz cans in the system and it is still not really cooling in the front, the rear is getting very cold @60 deg.F and below.
front is only getting down to 70deg.f. measured at the center vent and one of the roof vents (rear).
low side pressure is @55 and high is @250. with an ambient outside temp@85 deg. no gauge fluctuation indicating and issues.
2 questions are this:
where should the gages be?
side note here on my 2002 silverado the gauges read 50 on the low side and 250 on the high side ( I checked them for a reference)
and how much freon should the system hold?
the label under the hood is messed up and you cannot read anything on it...

thanks for your help
Link Posted: 7/18/2010 7:30:22 PM EDT
Link Posted: 7/19/2010 2:28:37 AM EDT
Thanks for the reply!
I have a set of ac gagues with an oiler so I can add more oil and freon,ill have the wife pick up some more today and see how it turns out.
Link Posted: 7/19/2010 3:18:14 AM EDT
did you pull a vacuum on the system before charging? if not you are wasting time and money.
Link Posted: 7/19/2010 9:03:40 AM EDT
Yes vacuum was pulled and it checked out good.
Link Posted: 7/19/2010 1:09:02 PM EDT
I used to know an AC guy who taught me a lot.  He believed in holding a vacuum on the system for at least 1 hour and really prefered 2 hours.  I would say that 10-15 mins is not enough.
Link Posted: 7/19/2010 1:36:59 PM EDT
Link Posted: 7/19/2010 7:34:31 PM EDT
What does the low side read with the engine at about 1500-2000 rpm?


Rule of thumb that I was taught that seems to work pretty good is.

Ambient temp times 2 + 10% for the high side pressure.

So 85 * 2 is 170 + 10% is 187. But if engine is at low idle and you aren't getting a good airflow then pressures will be higher thus the reason to elevate engine RPM.
Link Posted: 7/20/2010 4:45:10 AM EDT
Link Posted: 7/20/2010 5:37:04 AM EDT
Shop said comp was toast over 300 on high side...
Almost 2 hundred k on the odometer and she uses the air all the time.
So far so good blowing cold now with no issues, iadded more freon last night and the pressure was @50 on the low and 225-250 on the high at idle
Link Posted: 7/20/2010 6:27:20 AM EDT
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