A/C recharge pressure

[yeeha68]

My A/C got warm and eventually stopped last week and I am lost. (98 boxster) I think the compressor is still kicking in, as I can hear the lag in the motor when I turn it on. I thought maybe the R134a was low so I checked the pressure. This is what stumps me. I used a simple gauge and refill can (R134a PAG) but when I hook it up to the low pressure line it shows a pressure of over 100lbs. That would be way out of line, would it not? I keep hearing that an A/C recharge is simple and straight forward, but I need some guidance. Can anyone give me an idea of what’s going on with the pressure? Should it be that high? According to the gauge 35-40 is where it needs to be.

[fil756]

My A/C got warm and eventually stopped last week and I am lost. (98 boxster) I think the compressor is still kicking in, as I can hear the lag in the motor when I turn it on. I thought maybe the R134a was low so I checked the pressure. This is what stumps me. I used a simple gauge and refill can (R134a PAG) but when I hook it up to the low pressure line it shows a pressure of over 100lbs. That would be way out of line, would it not? I keep hearing that an A/C recharge is simple and straight forward, but I need some guidance. Can anyone give me an idea of what’s going on with the pressure? Should it be that high? According to the gauge 35-40 is where it needs to be.

It sounds like the pressure your reading (100psi) is probably the static pressure. static pressure is the pressure read when the compressor is off and both low and high sides are equalized. depending on ambient air temp that sounds like a good static pressure so i dont think that your system needs to be charged. sounds to me like the compressor isnt running. you should notice a click sound when the compressor engages(at least on most cars). sense porsche engines are well hidden its probably hard to hear.

if your compressor is running and your pressure on the low side is 100psi you either have a bad compressor (not compressing) or maybe a restriction (somewhere between the service fitting and compressor) restrictions are most common at the oriface or expansion valve. im unfamiliar with porsches a/c system and its hard to diagnose without the high side pressure.

35-45 psi is about right for the low side the high side should be about 200 psi both when the compressor is running. pressures are relative to ambient air temp as well as condenser and evaporator efficiency. there are other factors that effect pressures too like air flow but that is roughly what they should be.

anyway thats a lot of info but if i was you i would double check to see if your compressor is running.

hope that helps

phil

Edited August 7, 2006 by fil756