Help tracking A/C problem

[87turbolook911]

My compressor is not getting 12V when I turn the fan and a/c knobs all the way to the right.

If I jump the wire at the compressor with 12V , the A/C works fine. Just can't turn it on or off from inside the car.

Any ideas?

[ruf-porsche]

Does the blower motor for the evaporator come on when your turn the two switch all the way over to the right? If not check the fuse in the fuse panel and the a/c relay in the smuggler box.

I had a bad relay and replace it with one from Rat Shack (30 amp 12Volt). I brought the Porsche relay from Pelican. $5.00 for rat shack vs. $22 plus shipping from Pelican.

Oh by the way don't run the compressor with the lid open too long, or else you gonna pop a line somewhere. The rear condensor needs air flowing through it or else the high side pressure builds up enought that it's gonna pop a line.

[Joeaksa]

If you can read a wiring diagram I have some scanned from the Up Fixing der Porsche on this subject I could email you.

Also, have seen several A/C switches that were arc'ing inside. You might take the switch out and look at the back side and see how it looks.

Joe

[87turbolook911]

Ruf,

Yes the blower motor comes on when I turn the switches to the right. But it just blows air (not cold).

By the way where is the smuggler's box? I did buy a relay from Pelican already. Just don't know wher it installs.

Also thanks for the advice on not running the A/C too long with the lid up.

Joeaksa,

I would appreciate you forwarding the wiring diagram to me. How do you tell if the switches are arcing on the inside?

[Joeaksa]

87Turbo (what is your name pls?),

Take a look on the back of the switch and the two that I have seen were badly discolored in the terminal area. Board was brown and both of them had one or two terminals that were darker or even black from the heat.

Busy helping a friend move today. Pls send me your email and I will send it all along, and if I get time will take a picture of the switch to show you what these looked like.

Joe

joeaksa@attglobal.net

[87turbolook911]

I'll have to check mine this weekend.

Vu

[ruf-porsche]

Originally posted by 87turbolook911
Ruf,

By the way where is the smuggler's box? I did buy a relay from Pelican already. Just don't know wher it installs.

Also thanks for the advice on not running the A/C too long with the lid up.

Remove the carpet in the front trunk. you will see what appears to be a trap door with a lock(?) that some redneck might had made to lock his trailer home (this is what is know as German Design?). Open the trap door and you will see the blower and evaporator for the a/c. If you look around you will seem a relay mounted with a nut to the side wall.

Remove the nut that hold the relay and remove the relay from the smuggler box, don't disconnect any of the wire yet. THe relay should have number for each terminal. Remove one wire, note the terminal number and place it on the same terminal number for the new relay. after all the wires are on the new relay, start the car and test the a/c. If the compressor is working you have solve the problem if it isn't working, then it wasn't the relay.

Another problem could be the temperature switch on the left side of the console. I think it has a capillary tube, the switch is used to cycle the compressor on and off.

[Joeaksa]

Vu,

Home now and can email you the article. Pls shoot me your email.

Its a very good article and the relay Ruf mentions is one of the biggest problem areas.

Joe

[rick conrath]

If the temperature switch from the capillary tube goes bad, it won't send a signal to the compressor.

Rick '78 930

[87turbolook911]

I replaced the relay...the compressor still didn't turn on.

Now how do I check the temperature switch from the capillary tube??

Anything else to check?

[mussberger]

Check the continuity of the wiring all the way back to the switch. Thats what I found bad.

[ruf-porsche]

You can check if there is voltage going thru the temperature switch. You can use a test light or a volt meter. For a test light clip the wire to a good ground and use the end that look like an ice pick and touch each terminal of the temperature switch ( the fan motor switch for the a/c should be on. If the light light up on both terminal then the clutch should be receiving current. If the light light up on only one terminal and not the other than the switch is defective.

See the following site for a electrical diagram for the a/c in a Porsche.

http://www.pelicanparts.com/911/911_Parts/Electrical/911_electrical_82SC_AC.jpg