Automotive Air Conditioning Information Forum (Archives)

Provided by

We've updated our forums!
Click here to visit the new forum

Archive Home

Search Auto AC Forum Archives


kapilamuni on Wed August 10, 2011 7:07 AM User is offline

Year: 1998
Model: P38
Engine Size: 2500cc
Refrigerant Type: R134a
Country of Origin: Sri Lanka


I noticed that the back of the compressor there is a label saying that

High pressure - 3.53 MPa
Low pressure - 1.87 MPa

Is this possible? are these maximum possible pressures on each side?
when converted to PSI the figures are 512 & 271 respectively.

Also, I would like to know whether it's possible to collect the gas in a fully operational system( of course with engine off), through a gauge set connected to an empty tank?
Well I want replace a defective pressure switch,( new one fitted 2 months ago) which slightly leaks oil whenever the AC is on. Since here we don't have recovery machines, if I can't collect the gas it will be wasted if I'm to replace the p/switch. Again I'll have to pay for re-gassing.

thanks & regds


GM Tech on Wed August 10, 2011 7:43 AM User is offline

look at your new switch-- does it have a depressor in the middle where it attaches to the line or component? If so- no need to de-gas your system. If switch is leaking at base, a new o-ring is in order, not the entire switch....

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......

mk378 on Wed August 10, 2011 8:49 AM User is offline

Numbers on the compressor nameplate are rated absolute maximum (burst) pressure, they mean nothing with regards to normal operation other than that operating pressure would be much lower. Evaporators typically burst around 200 psi, so when leak testing with inert gas keep the pressure well below that even though the compressor says it can take 270.

Even with a recovery machine it is not possible to recover and replace 100% of the charge, you would still need to buy and add some new refrigerant after working on the system. It is possible to get most out without a machine by cooling the tank to zero degrees F or below, this will cause the refrigerant to come out of the car and condense in the tank. Tank and lines must of course be cleared of air first with a vacuum pump.

Edited: Wed August 10, 2011 at 8:51 AM by mk378

kapilamuni on Wed August 10, 2011 10:19 PM User is offline

Many thanks.

The pressure valve does not have a 'de-pressure switch' on it. It attaches direct to the drier.
The leak is from the wire connector on it. Is there a way out, without depressurising the system?

I can get the tank & lines vac'd. Then try to collect the gas even without starting the car, I hope.
Can i do this from any side, I mean high or low?

Yes, finally i will have to add a little amount of gas to compensate the losses. But then I'll be saving at least 50% of the cost.



Back to Automotive Air Conditioning Forum

We've updated our forums!
Click here to visit the new forum

Archive Home

Copyright © 2016 Arizona Mobile Air Inc.