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Topic: 88 Cougar Ac clutch wiring harness. (Read 999 times) previous topic - next topic

88 Cougar Ac clutch wiring harness.

Greetings.
The wiring harness just prior to the AC clutch has a diode (pair?) that shows shorted between all four wires with a VOM. My Haynes manual does not show this circuit. I have been unable to locate a shematic or part, local Ford dealer says no longer supported, local parts store does not show it, local junk yards either cut the harness or crush cars after a certain time frame.

My questions are:
1. What is the purpose of the diode/s?
2. Can this part be safely bypassed.
3. Can substitute diode/s be used, if so what values?
4. Reliable source for scematic or part.

Any help would be appreciated. Thanks.

88 Cougar Ac clutch wiring harness.

Reply #1 –
Quote from: damien;222491
Greetings.
The wiring harness just prior to the AC clutch has a diode (pair?) that shows shorted between all four wires with a VOM. My Haynes manual does not show this circuit. I have been unable to locate a shematic or part, local Ford dealer says no longer supported, local parts store does not show it, local junk yards either cut the harness or crush cars after a certain time frame.

My questions are:
1. What is the purpose of the diode/s?
2. Can this part be safely bypassed.
3. Can substitute diode/s be used, if so what values?
4. Reliable source for scematic or part.

Any help would be appreciated. Thanks.


The purpose of the diode is to keep the contacts in the pressure switch from burning up due to excessive arcing

To test with an OHM meter the diode must be isolated from the circuit. One side of the diode must not be connected to anything.
If you have a digital meter you may have a special set-up for testing diodes. For instance on my Fluke you push in both the 20meg and the 2 ohm range buttons.

The diode should have high resistance in one direction and low resistance in the other direction.( Reverse the test leads)

88 Cougar Ac clutch wiring harness.

Reply #2 –
I have removed this section of the wiring harness from the car. My meter has a diode test feature. There is low resistance in both directions. Initial ohm check across the pins of one connector showed a short. I cut the wires to ensure isolation and all four wires are electrically common to the others through the diode.

88 Cougar Ac clutch wiring harness.

Reply #3 –
If the diode has low resistance, in the against the arrow direction, it will cook or blow fuse #17 or both.
If your wiring matches this '87 version, you should be checking between the BK/Y and the BK wire sides.

Do you have another diode you can test, or an buttstuffog meter? Just to make sure your meter is not fooling you.

You must have some reason for being here in the first place.

88 Cougar Ac clutch wiring harness.

Reply #4 –
If you have a test light, hook it in series with the diode and touch it across the battery. The light should light with the diode in one direction and not in the other.

88 Cougar Ac clutch wiring harness.

Reply #5 –
My diode block does match the 87 version. Thanks for the schematic.
The original problem is that the AC clutch does not engage. The pressure switch in the acspoogeulator is made and there is voltage prior to the diode block. If I hook power straight to the clutch terminals, it will engage.
I have two diodes from Radio Shack and the diode test function of the meter shows 0.45 vdc for one polarity and OL vdc for the other.
The Cougar's diode shows 0 vdc for both polarities.
I am fairly certain that the diode is shot. Where can I obtain a replacement, or what specifications would a substitute diode need to be?

88 Cougar Ac clutch wiring harness.

Reply #6 –
The only one I could find googling around is for a Corvette.

http://www.ecklers.com/product.asp?pf_id=44831&dept_id=1135&cm_mmc=Froogle-_-Electrical+-+Harnesses+%26+Wiring+-+ALL-_-44831-_-X

You should be able to make it work for you. I couldn't find any specs for the diode.

I don't understand why you didn't blow fuse 17 since your diode tests as shorted out.