Help - How to read AC pressures

[axl911]

All,

This is for a 993 with R134.

After hooking up the AC gauges on the high and low, am I supposed to rev to 2K RPM to read the pressure? And do I have to hold it there? Should the pressures drop after releasing the gas and allow the car to idle again (with AC compressor still on and running)?

The manual states that "the pressures specified in the diagrams must be reached after approx. 10 mins operations time at a speed of 2K rpm with the compressor switch on."

thanks,
anthony

[rattlsnak]

they are basically trying to make sure that it has had enough time to cycle and at enough RPMs to sustain a good pressure. the pressures will slightly vary (be slightly lower) from the different speeds, but not too dramatically from 2000 rpm to idle, but to do the test 'correctly', yes, you should read the guages at the proper RPM. You could just drive it down the road a few miles and then return, hook them up, raise the the rpm to 2000 and then read wha you got. You really dont have to sit there for 10 minutes, but either way is fine.

[axl911]

Thanks. I will read it again at 2000 rpm. According to the specs, I am too high. Will try to adjust for the correct pressure. Reading the pressures correctly is critical for this.

[rattlsnak]

Is it not cooling? there should be a chart to mate with the outside air temp as well, as that will make a difference. has someone put too much in? or has it been opened up? if thats the case, and you are unknown to what happened then its simply just easier to drain it and refill it with the correct amount.

[axl911]

It is cooling but not very good. I found a link on Rennlist which gave me the specs I needed. Looks like am way over pressurized on the R134.

This is a good writeup on troubleshooting the 964/993 AC system.

http://forums.rennlist.com/rennforums/993-forum/351059-complete-a-c-diagnosis.html