Headlights Inoperative
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500, 472, 425, 368 Discussion, Headlights Inoperative in Cadillac Engine Technical Discussion; I have a 1980 fleetwood brougham, which has the twilight sentinel headlight as well as the auto-dimming for oncoming traffic. ...
  1. #1
    spankey is offline Cadillac Owners Member
    Automobile(s): Cadillac
    Join Date
    Oct 2007
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    Headlights Inoperative

    I have a 1980 fleetwood brougham, which has the twilight sentinel headlight as well as the auto-dimming for oncoming traffic. Normally I drive with the lights on all the time, and recently I went to turn on the headlights, and the only thing that comes on now is the orange fog lights/running lights, and the tail lights, etc. All the blinkers and brake lights work fine, but I cannot get the headlights to turn on at all.

    I replaced the Guide-Matic Relay, since I thought that had something to do with the auto-dimming. Also replaced the headlight switch in the dash, because it was loose, but no luck.

    Prior to the problem, the auto-dimming headlights were intermittent. If I drove over bumps with the brights on, they would "chatter" and often quit working, so all I had left was the regular headlights (no brights).

    Any thoughts on the cause of this problem?

    Thanks,
    Daniel-

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  3. #2
    steelybill is offline Cadillac Owners Enthusiast
    Automobile(s): '85 Fleetwood FWD
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    Mar 2009
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    mich
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    Re: Headlights Inoperative

    My first suspicion would be a bad ground on the headlight harness, which should be somewhere up front near the radiator core support. Look around up front for some grounding points, like near the battery, etc The usual ground wire from the headlamp connectors is a black wire.
    You may have to un-wind some of that tape you mentioned

    There is also a feed-through connector on the firewall, usually near/below the brake booster. Those have been known to be a problem also. There is usually a hex-headed screw in the center, holding the connector and harness into the firewall side of the connector. The connector is usually full of black goo to keep moisture out. Make sure that hex screw is tight.

    There is a circuit breaker in the fuse panel (usually) that feeds the headlights. It's a plug-in silver colored thing , which is like a 30-amp rating. It may also be a problem.

    Hope this helps.

    BILL

  4. #3
    1980coupe's Avatar
    1980coupe is offline Cadillac Owners Connoisseur
    Automobile(s): 78 CDV, 79 CDV delegance, 80 CDV, 80 FWB 2dr delegance (rip)
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    Jan 2009
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    El Paso, TX
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    Re: Headlights Inoperative

    Hi there,
    I have your solution!
    I owned a FWB Coupe many years ago, 11 to be exact, and they gave out.(headlights) Now being younger then I did not know much so I hot wired them directly. I took a wire connected it to the positive side of battery and ran wire inside dash and I spliced the wire of the low beam headlights into the dash and when touched together lights came on. Now fast forward 11 years later, I own another 80 Coupe (deville) and the lights gave out. Now I know what and where to look with the help of my manuals and wiring diagrams.
    First, turn on lights, leave all that guidematic, sentinel off. Now, switch to your high beams, do they come on and only high beams and low beams out or all four headlights out? Check for power down by the steering column, thats where your dimmer switch is. Check with a 12 volt light tester at green and tan on both sides, if no light on tester then your dimmer switch is out. If lights up, go under hood and where the wire loom is that runs to the radiator support pull out the wires and check here as well to check for continuity. Now down by the charcoal canister pull out wires here and there should be a fusible link that melted. That's what went out on mine and I wired in a fusible link, the one with the little cover on it. There's no circuit breaker on fuse panel or the accessory panel; there is one in switch as indicated by my manual. I hope this helps and I explained myself. If you need further assistance let me know through here and I'll response with further details. Also I do not have internet at home but I'll try to go a WI-FI area with my laptop.
    Thanks
    Edgar

  5. #4
    1980coupe's Avatar
    1980coupe is offline Cadillac Owners Connoisseur
    Automobile(s): 78 CDV, 79 CDV delegance, 80 CDV, 80 FWB 2dr delegance (rip)
    Join Date
    Jan 2009
    Location
    El Paso, TX
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    1,112

    Re: Headlights Inoperative

    sorry forgot to subscribe to this, otherwise how am I going to know when you replied or other comments are posted.

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