a/c temp control
 

while it's not the season to worry about a/c...here in denver anyway..i have a question - i've always heard you should run the a/c occasionally in the winter to keep the oil on the seals - so i ran it about a month ago and everything seemed ok - outside temps in the 60's or 70's - i tried it again this week and the compressor would not run - so i'm wondering how does the temperature control in the dash actually work - it has numbers from 65-85 on the head unit - would the compressor NOT spin if the temp is below 65 degrees outside - it was pretty cold when i tried it..about 40 - so does the head unit work so if i have it set to 65 degrees and it's already colder that that in the car it doesn't energize the compressor clutch - or do i have a problem with the a/c - it's been pumping out ice cold air for a year and a half so i'm not sure of what could have happened in the last month or so - thanks and happy holidays to all

Here is a good overview by Wally on Jeannie and David's site:
https://www.928gt.com/T-WallyHVAC.aspx

and Greg's site has lots of good stuff
Porsche 928 Maintenance Tips and Procedures


Do some reading first so you become familiar with the components and common failures:

low refrigerant level, (try jumping the low side switch or send power directly to the clutch), not enough amps from the control head relay, a good clutch coil is 3 ohms nominal,
etc

On the Rennlist seek out Dr Bob

Cheers and have a Merry

Griff

thank you kuehl for the link - i used it to track down the pressure sensor on the dryer - i pulled the wires off it and connected them together and the compressor clutch did engage - so i metered the pressure switch and it showed continuity - put the wires back on and the a/c is blowing ice cold - so... bad connection on the wires at pressure switch - felt tight and they looked clean - anyway i'm happy it was something simple - everyone here knows simple fixes don't come along often on these cars - happy new year to all