Mark

I just R&R my AC compressor that had burned up the clutch. (I bought a used compressor from Kibort - I believe it came off the Holbert car - so a piece of "928 history" now on my shark!)

I am not getting any voltage to the pigtail where the compressor wire plugs in. I jumped a 12v source directly to the compressor - and all is fine - but checking the voltage on the little pigtail 12v+ source that hangs down in front of the PS TB cover yelds nothing.

Any ideas?
(The fuse is good! - And the light on the AC button comes on when depressed)

FlyingDog

I believe there is a relay for it (like everything else on these cars), but I haven't dug around in the A/C system yet so I could be wrong.

Mark

I thought so, too - even checked my relay chart TWICE! Nope...

I'll double check with the 928spec online charts...

ViribusUnits

The relay for the a/c is inside the A/C control unit head.

It's rather undersized too, so a new head unit isn't very helpful.

Suggest finding the write up and replaceing the replay with a bigger unit.

Good luck.

Mark

Hmmm...relay # XVIII on 928spec shows it is a "A/C Condensor/Radiator Fan".

I'll check it. My fans work...BUT - we have long thought that the were somehow "hardwired", as run continuously while the ignition is on...and never stay on after the key is turned off. (when she's hot - i always sit a couple of minutes with the key on and engine off to get some post-drive cooliong)

Mark

Thanks, VB...you posted while I was typing, I'll check that also.

Ed MD

Go to the Nichols site, http://www.nichols.nu/tips.htm, and then to climate control, then "Compressor Clutch Power Relay, Story #2" by Dr. Bob. Excellent diagnostics and repair. Ed M

SharkSkin

You didn't mention putting freon back in... It could be that the low pressure switch has locked the compressor out. Even less likely, the freeze switch is kaput. Anyway, those are two easy things to check before you rip into the console. IIRC the low pressure switch is buried in front of the radiator on the passenger side. The freeze switch is under the rainshield at the base of the windshield. I think you should be able to see the signal from the console AC switch at one of the freeze switch terminals.... but check the schematic to be sure.

HTH

Mark

Well - no I didn't put any in, as i thought the compressor needed to be running to fill it! HMMM....

NickT

Ran through this with my '88. The "little blue" relay in the control head is way undersized for the job. Over time the contacts pit and no longer make a good enough contact to pull the clutch.

It's a fairly simple task to install a secondary heavier duty relay to drive the clutch. All the little blue one has to do is pull the secondary. I'll take some pics of how I did mine and post them here. A simple job, less that 30 mins.

GlenL

Have you tried jumpering the lines to the pressure switch? Don't run it too long like that our you can seize the compressor.

Mark

I think I'll try this - and just test for voltage at the compressor feed wire, so as not to risk all the work to R&R the compressor!

NickT

OK hope this works... This is for a '88 S4. PLEASE CHECK YOUR WIRING BEFORE MOVING AHEAD. This is just how I did mine, yours may differ... The picture is my scribble on the schematic, hope it makes sense.

1. Remove the passender side side panel of the tunnel.
2. Locate a 4 wire connector, T29.
3. Pin #2 is the +12V to drive the clutch. Check this with a meter to make sure it is the correct one. Mine was Violet/Yellow.
4. Cut it on both sides of the connector.
5. Connect the tail coming from the head unit to the coil of the new relay.
6. Attach the other side of the relay coil to a solid ground.
7. Connect one side of the new relay's contacts to a +12V source. Pin #1 on the down stream side of the connector is what I used.
8. Connect the other side of the relay contact to the wire leading to the AC clutch.

Essentially at this point you are done. Test everything to make sure it works. Neaten everything up and and reinstall all panels.

The relay I used was a heavy duty relay SPDT that I found at my local NAPA store. I'll try and get a pic of the installation.

WallyP

Mark,

If the A/C system is leak-free (checked during the vacuum pull-down - which is MANDATORY), just dump the first can in as liquid (can upside down) without the compressor running. Try the second can that way - and when the refrigerant no longer flows into the system, turn the can right-side up, wait a couple of minutes to make sure that there is no liquid left in the compressor, the fire up the engine and turn the compressor on to put the rest of the refrigerant in.

Your fan ("fans"? usually just one on an '85) is wired incorrectly. This adds noise and reduces mileage slightly, but will improve A/C performance a bit.

The fan should be controlled by:
- A coolant temp switch on the forward lower face of the left radiator tank.
- A fluid temp switch mounted on the transmission (autos only).
- A refrigerant temp switch mounted on the stem of the receiver/dryer (not very effective).
All of these work only when the ignition switch is on.
- An air temp switch mounted on the top of the intake manifold. This one works with the ignition off, to provide cool-down after shut-down, if the engine is very hot.

Mark

Thanks, Wally...more stuff to try....

As to "fans"...I have long-ago replaced my viscous fan and the OEM electric one with a couple of Haydens in a push/pull config. Even prior tho, my FAN ran constantly.