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Topic: No Power to A/C Clutch? (Read 2603 times) previous topic - next topic

No Power to A/C Clutch?

I was trying to fix one problem yesterday with the hesitation, and during it all, another one started.  Guess it always goes like that though. :dunno:  I'm not getting any power to the AC clutch or the diode before it, but there is power at the pressure control switch.  The thing thats got me boggled is, if it was a short, wouldn't it blow the fuse?  If anyone has had a similar problem, maybe you can help me out.  I checked my electrical book in my shop manuals, and it said it might be the blower control switch, but the blower comes on fine.  I'm going to try to get it by the dealership tomorrow to see if they can fix it.
Fly on Thunderbird, Fly! Operation Buy Back My Tbird or one like it funding: $0


Re: No Power to A/C Clutch?

Reply #1
Matt,

So you know you have power at the pressure control switch , but if you jumper the switch the clutch still doesn't engage?  Is that right?

I didn't think there was really anything between the two?

Re: No Power to A/C Clutch?

Reply #2
We tried jumping the switch and still nothing happened.  The problem is so strange...haha  I had to take a break from it yesterday cause it was driving me insane.  But yes, there is indeed power at the switch.
Fly on Thunderbird, Fly! Operation Buy Back My Tbird or one like it funding: $0


Re: No Power to A/C Clutch?

Reply #3
The voltage is fed from the pressure switch to the A/C cut out relay(it is mounted low just in front of the passenger side strut tower). The relay is fed 12v on the red wire and ground is provided by the EEC. So your problem is oone of the following..

1 bad relay(probably)

2 no voltage fed to the relay(on the red wire)

3 wiring problem back to the EEC(orange/Lt Blue wire, if grounding this wire engages the comp, the problem is either #3 or #4)

4 bad EEC(I say thats not really likely but it does happen).

Re: No Power to A/C Clutch?

Reply #4
I was trying to find the relay yesterday, but I couldn't locate it.  I traced the wire down the best I could and wasn't able to spot it.  My uncle had mentioned the same thing too (he works at a ford/lincoln dealership) and he said it was probably the relay, but when he couldn't find it he mentioned something about why it didn't have one...I wish I could remember what he said now.
Fly on Thunderbird, Fly! Operation Buy Back My Tbird or one like it funding: $0


Re: No Power to A/C Clutch?

Reply #5
My 85 5.0 had the same problem and it turned out to be the blower motor control which has a big heat sink on it and is installed in the fan blower housing.  A trace had blown on the controller board which fed power to the low psi cutoff switch then to the a/c clutch.  Not sure if the 87s have the same setup.
1985 30th anniversary, original owner

Re: No Power to A/C Clutch?

Reply #6
i had the same problem a few years back and  it was the relay.  i was gonna say that but tom spoke b4 me so. hopefully thats it for you. oh and make sure they give you the rite one i had to go back bc it wasnt rite. ez fix though

Good luck
trick flow street heat intake , 24lbs injetors, ported GT-40's (Chip) long tube headers. and a Performance Automatic C4, with a hurst shifter!

Re: No Power to A/C Clutch?

Reply #7
Quote
The voltage is fed from the pressure switch to the A/C cut out relay(it is mounted low just in front of the passenger side strut tower).

Quote
I was trying to find the relay yesterday, but I couldn't locate it.


Is this it?
Death awaits you all with nasty, big, pointy teeth.

1988 5.0 Bird, mostly stock, partly not, now gone to T-Bird heaven.
1990 Volvo 740GL. 114 tire-shredding horsies, baby!

Re: No Power to A/C Clutch?

Reply #8
Ummmm, looks like Master Blaster found it with no problem....

Re: No Power to A/C Clutch?

Reply #9
Yeah it kinda sticks out there all by itself.  I had a similar problem with my car right before CJ this past summer.  The insulation on the wires was all dryrotted right near the plug that goes into that relay.  I had to repair them and when I plugged it back in everything worked fine.
-Jim
1987 Cougar LS 5.0