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Thread: '91 CV no taillights during breaking

  1. #1
    Member Hill185's Avatar
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    Default '91 CV no taillights during breaking

    So, the taillights work for turn signals, hazards, however when I step on the break only the high mount/3rd brake light illuminates. Fuses/bulbs appear intact, id assume its not the break light switch as the 3rd brake light illuminates. Any ideas ? Thanks for any tips.

  2. #2
    all the CFI are belong to me
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    This is most likely a problem with your turn signal switch (multifunction switch), and more specifically, probably the hazard function of the switch.

    Because the turn signals and brake lights share the same bulb, the turn signal switch (or hazard switch) has to interrupt the brake light voltage to enable the voltage to be cut on and off by the flasher. Since your problem is both sides, I suspect the hazard switch.

    Aggressively pull out and push in the hazard switch a few times, and re-test. If the problem is gone, now it may be fixed for a while, or maybe forever. If it does not work, my next step would be to inspect the wiring at the turn signal switch, and consider replacing it.

    If it did work, I'd then try to make it break again by doing things like wiggling the hazard button or smacking the bottom of the steering column. If the lights stop working again, I'd replace the switch even if you can wiggle it into working again.

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  3. #3
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    Quote Originally Posted by kishy View Post
    This is most likely a problem with your turn signal switch (multifunction switch), and more specifically, probably the hazard function of the switch.

    Because the turn signals and brake lights share the same bulb, the turn signal switch (or hazard switch) has to interrupt the brake light voltage to enable the voltage to be cut on and off by the flasher. Since your problem is both sides, I suspect the hazard switch.

    Aggressively pull out and push in the hazard switch a few times, and re-test. If the problem is gone, now it may be fixed for a while, or maybe forever. If it does not work, my next step would be to inspect the wiring at the turn signal switch, and consider replacing it.

    If it did work, I'd then try to make it break again by doing things like wiggling the hazard button or smacking the bottom of the steering column. If the lights stop working again, I'd replace the switch even if you can wiggle it into working again.
    QFT. This. Known issue with all vehicles with this type of setup (Re: American vehicles).

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  4. #4

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    I was just dealing with a similar issue on my '78 LTD wagon. I second the multifunction switch. You can see how the brake light feeds through the switch on the wiring diagram. The switch isn't setup the same as on my LTD, but the circuitry is pretty similar still.
    1978 Ford LTD wagon, 351M
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    Member Hill185's Avatar
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    It’s funny because I Just replaced that multifunction switch twice lol. The original was cosmetically not great. Purchased an NOS one via eBay however that one acted funky. Headlights only worked on high beam. So got an aftermarket multi switch, and this is the issue I’m getting from the 2nd new switch…lol

  6. #6
    Still Wrenchin'! friskyfrankie's Avatar
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    Quote Originally Posted by Hill185 View Post
    It’s funny because I Just replaced that multifunction switch twice lol. The original was cosmetically not great. Purchased an NOS one via eBay however that one acted funky. Headlights only worked on high beam. So got an aftermarket multi switch, and this is the issue I’m getting from the 2nd new switch…lol
    Can you find an OEM switch?
    What I Own: 1993 Mercury Grand Marquis GS
    What I Help Maintain: 1996 CV / 1988 CV / 1988 Tempo

  7. #7
    Still Wrenchin'! friskyfrankie's Avatar
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    Quote Originally Posted by Hill185 View Post
    It’s funny because I Just replaced that multifunction switch twice lol. The original was cosmetically not great. Purchased an NOS one via eBay however that one acted funky. Headlights only worked on high beam. So got an aftermarket multi switch, and this is the issue I’m getting from the 2nd new switch…lol
    Can you find an OEM switch? May or may not be at a reasonable cost but may be the best move as opposed to buying several aftermarket ones.
    What I Own: 1993 Mercury Grand Marquis GS
    What I Help Maintain: 1996 CV / 1988 CV / 1988 Tempo

  8. #8
    Member Hill185's Avatar
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    It’s funny, the first replacement switch was NOS OEM Ford part. But I may try and find another and see what happens.

  9. #9
    Still Wrenchin'! friskyfrankie's Avatar
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    Was the OEM you bought new or used?
    What I Own: 1993 Mercury Grand Marquis GS
    What I Help Maintain: 1996 CV / 1988 CV / 1988 Tempo

  10. #10
    I'm an air-conditioned gypsy gadget73's Avatar
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    check the connections, maybe something is loose. Since the third light works, the brake light switch itself must be OK, and the signal is failing between the brake light switch and the output from the multifunction. I don't know if there is a connection between the brake light switch and the multifunction switch to check.

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  11. #11
    Member Hill185's Avatar
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    This was the issue thank you! Popped the the steering column cover off, checked and reinstalled, taillights now operate and intended. Thanks again

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