A/C clutch doesn't operate after a shortcut in relay replacement
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RWD 19xx-1984 DeVille and Fleetwood,
1985-1996 Fleetwood and Brougham Forum Discussion, A/C clutch doesn't operate after a shortcut in relay replacement in Past Cadillac Vehicle Discussion; Hy all, A new question about the A/C system of our beloved cads ! I've replaced the blower relay on ...
  1. #1
    jeff_herry is offline Cadillac Owners Member
    Automobile(s): 1978 EFI fleetwood brougahm d'elegance
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    A/C clutch doesn't operate after a shortcut in relay replacement

    Hy all,

    A new question about the A/C system of our beloved cads !

    I've replaced the blower relay on my 1978 fleetwood some weeks ago. But due to the fact that the old relay was not appropriate and was connected with "long wires" at anither place of the relay center, I've created a shortcut while taking the old relay off.

    After replacement, the new relay is perfect, and the blower is OK at any position of the control panel (from off to def). But unfortunatly, the A/C compressor which is in good shape and was Ok before this problem, refuses to operate anymore. When I put the control panel on "low" or "auto" or any other position that need the compressor, I cannot hear the sound of the electric clutch. And of course the compressor is not in motion.

    I've checked the fuse, that is also linked to the generator light on the dash board, as says the shop manual, but the fuse is OK.

    Is there a relay that protect the clutch or the compressor that could have had some problems due to my shortcut? If yes where is it located? Or is there anything to do to check if the compressor clutch is OK or any other part of the A/C electrical system ?

    Just let me know what yout think about this !
    Thanks. Jeff

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  3. #2
    Robin Banx's Avatar
    Robin Banx is offline Cadillac Owners Fanatic
    Automobile(s): 1983 Fleetwood Brougham
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    Re: A/C clutch doesn't operate after a shortcut in relay replacement

    First, test the clutch by running a small hot wire from battery positive terminal to the positive pin on the clutch. Make sure to leave the ground wire in place when you test it. A quick touch with the hot wire to the pin on the compressor will be enough to engage the clutch with a smart "snap". If that is ok, look to the power source for the clutch.
    Another way to test the clutch would be to put a test light to the positive wire in the clutch harness while simulating operation. Key on, A/C on, blower on high. Good luck. I hate electrical gremlins!!

    Cheers.......R

  4. #3
    jeff_herry is offline Cadillac Owners Member
    Automobile(s): 1978 EFI fleetwood brougahm d'elegance
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    Thread Starter

    Re: A/C clutch doesn't operate after a shortcut in relay replacement

    Thanks Robin, for that is a very good idea.

    I've had a look on the shop manual, and I saw your method explained in the "compressor electrical problems" chapter. But I'm not sure concerning the location of the positive terminal of the clutch. When in front of the car, is it the left terminal or the right ? I will have a look tonight to see the color of the wires at the clutch coil terminals.

    HAve a good day.
    Jeff!

  5. #4
    jeff_herry is offline Cadillac Owners Member
    Automobile(s): 1978 EFI fleetwood brougahm d'elegance
    Join Date
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    Angouleme / france
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    Thread Starter

    Re: A/C clutch doesn't operate after a shortcut in relay replacement

    Ok,
    I've checked the clutch with you method. The "snap" is OK when putting the positive terminal in contact with the battery.
    I've also simulated operation at high and other blower speeds and there is no power in any case.

    So to summary, the blower relay is OK, the fuse is OK, the clutch is OK. But I don't know how to test the power source from the control panel to the clutch. I was thinking about something. Would it be possible to create a specific harness in order to power the clutch? I mean, from a button linked to the battery then going to the thermal switch that detects the ice inside the evaporator and the low pressure switch ? In this condition, it would be possible to manualy power the clutch when the control panel is in a A/C position. Or may be I could find the contact on the control panel that power the clutch. What do you think about this ? good or bad idea?

  6. #5
    Robin Banx's Avatar
    Robin Banx is offline Cadillac Owners Fanatic
    Automobile(s): 1983 Fleetwood Brougham
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    Re: A/C clutch doesn't operate after a shortcut in relay replacement

    The A/C clutch worked before you created your "shortcut". What (if anything) would happen if you put it all back the way it was prior to the shortcut?? You mention its being connected and working properly but the wires were too long and not of a heavy enough gauge. Is this not factory original wiring then? Beyond that and without being able to see it, that's about all I can think of.

    Cheers.......R.

  7. #6
    jeff_herry is offline Cadillac Owners Member
    Automobile(s): 1978 EFI fleetwood brougahm d'elegance
    Join Date
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    Thread Starter

    Re: A/C clutch doesn't operate after a shortcut in relay replacement

    Well, when I bought the car, the blower motor was running only in def position. After checking the A/C system, I've discovered that the original relay has been replaced with an european single pot relay. Due to the fact that the car was in France, and the previous owner had no possibility to order an original relay in the US. To adapt the european relay to the car, the previous owner created 4 wires taking power on the relay center and going to the european relay.
    At this moment, the A/C clutch was OK, and the compressor ran in Def position, cooling the air normally. When I' decided to replace ce european relay with an original US one, and due to my awkwardness, I created an electric short circuit between 2 wires. When I put in place the US relay, the blower motor recovered the good speed for each speed selection on the control panel. Except the clutch that refuse now to operate. That's my story.
    I supppose that I've created an issue in the power wiring of the clutch, but I don't know where. That's my issue !
    Well I will try to put another control panel, as it is the direct junction from the fuse to the clutch.
    I will let you know !
    See you and thanks again.
    JeFF

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