A/C stopped working...need help !

Ron Egan · 04-02-2003, 10:53 AM

Ran my A/C this afternoon on the way to lunch. On the way back, turned the knob and no blower. Checked the fuse and it looked fine. What should I check next ?

Thanks,

Ron
'85 911 Targa

targa80 · targa80's Garage

Does the clutch for the compressor engage when you turn the AC on?

Ron Egan · 04-02-2003, 11:36 AM

Pat,

I didn't pay attention but now that you mention it...I don't think it did.

Ron

88911coupe · 04-02-2003, 11:48 AM

There is a safety mechanism that keeps the a/c from coming on if the freon level gets too low. Are you sure it's topped off completely?
later

rick conrath · 04-02-2003, 11:53 AM

The blower would work even if the freon were low. If the compressor is turning but nothing is coming out of the vent, the switch might be bad or you blew a fuse. If its blowing but just not cold, then that is a different issue.

Ron Egan · 04-02-2003, 11:59 AM

I get absolutely nothing when I turn the blower switch, irregardless of the position. Most likely a bad switch ?

APKhaos · 12:16 PM

The fuses have a nasty habit of building up a layer of corrosion on the end caps. Take the fuse out, and clean the end caps. Nothing too abrasive - a scotchbrite pad is fine. Take a good look at the fuse holder as well. Replace the fuse and test.

FWIW, with ignition on, the blower and front condenser fan should operate as soon as you turn the AC Fan switch from teh Off position. The clutch is another issue - its gated by engine running and pressure > minimum.

This has happened three times in two years on my 85 - twice [!] on the AC fuse, and once on the electic seat fuse.

targa80 · targa80's Garage

The 82 AC schematic is located on the Pelican web site I know it might not be exactly what you have but I bet it is real close.82 AC schematic
Battery voltage is supplied thru fuse 20 to reay AC contacts. The relay AC is energized when the ignition switch is on allowing battery voltage to the AC fan switch. the AC fan switch supplies battery voltage to the Clutch on the AC compressor. THere is a temp switch in the clutch circuit that opens if the temp gets to cold (tempadjust). At the same time battery voltage is supplied to the evaporator resistor unit /fan (cabin air) located in the passenger foot well/ smugglers box in trunk. The cooling fan motor is located in the front part of the trunk supplying air to the condenser behind the front bumper under the car.

1) If you have no air from the evaporator fan(cabin air) and the clutch on the compressor is not engaging then your problem is either in the relay AC or fuse # 20 or the ingnition switch is not supplying battery voltage to the coil of the relay AC.
2) If you have the clutch engaging on the compressor and no air blowing from the evaporator fan (cabin air) then your problem is only in the evaporator resistor unit/fan circuit.

rick conrath · 04-02-2003, 12:22 PM

The connector posts on the back of the switches are prone to failure and become loose. I have had several short out with age. The fuses are also troublesome.

targa80 · targa80's Garage

I have had several problems with my AC over the years and one was the wire coming off of fuse 20 had overheated and effectively became an open wire. I cut the wire back tinned the end with solder before reinstalling into the fuse holder. With a good multimeterand the schematic you should be able to isolate the problem. More than likely is is a corroded /overheated contact somewhere in the circuit. Do the obvious things first fuse and relays.

LeRoux Strydom · 04-03-2003, 01:20 AM

If the fuse is OK with clean contacts (check for voltage on both sides), then your a/c relay next to the blower unit in the smuggler's box is probably defective. See recent thread here.

LeRoux

ruf-porsche · ruf-porsche's Garage

Hey LeRoux Strydom

The relay was the problem why my a/c stop working. I got a new relay from Pelican and it came in a porsche box, but it's a little different from the relay I pulled out of the car. The old relay didn't have a fuse but the new relay has a fuse. Old relay was made in Germany, new relay is made in China.

I think the relay that I got at Rat Shack was closer to the old relay ie no fuse.

ruf-porsche · ruf-porsche's Garage

I think the fuse in the new relay is to prevent the the a/c harness from burning up in the event that the motor that cool the front condensor has seized. Older 911 does not have a fuse for the condensor fan motor and in some case there has been fires in the front trunk compartments due to the motor drawing so much current.