[polliviere]

I’m seeking any ideas that might help diagnose my A/C problem.



My compressor runs all of the time. The compressor clutch engages as soon as the engine starts and the fans come on a few seconds later. The unit will not turn off no matter what you do with the switch on the HVAC control. If you remove the a/c relay the clutch will not engage and thus the compressors not run. If you push the a/c switch with the a/c relay removed the a/c fans will run. When I put the relay in and start the car the a/c is cold.



Thinking that the switch was bad I replaced the HVAC control unit, this resulted in no change to the problem. Since I was replacing the carpet and had the interior stripped down I looked for any signs of bad wiring and found nothing. I can only think that the relay has failed in the closed position on the trigger circuit and is thus energizing the compressor as soon as the main power comes on. I have a new relay on order to replace the existing one but I also could be talking out my backside; I’m looking for smarter heads than my own that might offer suggestions.



Peter

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[jfrahm]

Check the defrost circuit. Sometimes running the defrost activates the AC compressor to dehumidify the air.

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[Gotter]

Exact opposite of my problem.... I push A/C and it's NEVER cold! <img src="/forum/images/smilies/968/wink.png" class="smilie" alt="" />

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[MB968]

Woops, the info originally posted (post below the line)was incorrect. The wire leading to the A/C clutch on the Mazda, and on the 968 is the positive lead, with the housing providing the ground. See my newer post below from 4/6.



____________________________________________



On my Mazda, the A/c clutch has 12 volts across the magnet coils all the time. The control circuit then grounds the coil when it wants it to engage and have the compressor work. So if the 968 works similarly, and if there it a short to ground on the wire running from the control circuit to the coil, it would stay on all the time. May not be the only reason this could happen, but worth a look.

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[DaveN]

I was going to suggest that the other day but I stopped my post because I ASSUMED the wire to activate the clutch would have 12V on it not gnd. But if it is like a Mazda (heaven forbid) then the single wire underneath that controls the clutch can easily short out to the frame with old, cracked insulation.

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[polliviere]

MB968 and DaveN,



Thanks for the input, I went back to the wireing diagram and have a question? I have been thinking that the wire running from the a/c relay through the pressure switch and then to the a/c clutch was posative, but what you seem to be saying is that this line might be a ground, or negative line. If this is the case would not a short in that line cause the clutch not to ingage?

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[Ryan]

I am with Joel on the defrost switch idea. Did you check this? That is the only thing independent of the main controls that will make the A/C run no matter what.

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[MB968]

[quote name='polliviere' timestamp='1333714248' post='124633']

MB968 and DaveN,



Thanks for the input, I went back to the wireing diagram and have a question? I have been thinking that the wire running from the a/c relay through the pressure switch and then to the a/c clutch was posative, but what you seem to be saying is that this line might be a ground, or negative line. If this is the case would not a short in that line cause the clutch not to ingage?

[/quote]



Heah, looks like I was leading you down the wrong path. Took a look at the '92 968 wiring diagram and in quadrant A-24 it shows the compressor as "housing to gound". So the wire coming into the clutch would be the positive as you originally thought. Sorry for any inconvenience.



And, I looked at my old Mazda wiring diagrams and it is connected the same way, with the wire coming in as the positive. It's been about 10 years since I did all the rewiring to run the standalone on the Mazda, guess my memory isn't as good as it use to be.



I'll edit my above post so if anyone searches they don't get the wrong info.

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[polliviere]

MB968,



No problem, each suggestion moves me closer to a solution.

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[Scott Collins]

Hey friends,



My a/c compressor is "kaput".

Car is hot and starting to fog up inside. Not good.....



Anyone have a good source on a new or reman unit. especially if you have personally installed one with positive feedback? Thanks for chiming in.



-Scott

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[94'968]

Pete at RSbarn gave me a guys phone number for parts and i got a used compressor from him last year. cant remember the price, but it was GOOD! Forgot to save the number, so id just call pete and he'll hook you up.

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[Scott Collins]

Duh! Don't know why I didn't already do that...... Thanks - and thanks for the pads. They go on the car next week. Cheers! -Scott

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