75 Deville Illuminated Entry Troubleshooting
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  • 2 Post By cadillac kevin
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The Classic Cadillac Forum Discussion, 75 Deville Illuminated Entry Troubleshooting in Past Cadillac Vehicle Discussion; Just picked up my 75 Sedan DeVille with 44K miles last week. Working on ironing out the minor issues I ...
  1. #1
    shwhitley's Avatar
    shwhitley is offline Cadillac Owners Member
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    75 Deville Illuminated Entry Troubleshooting

    Just picked up my 75 Sedan DeVille with 44K miles last week. Working on ironing out the minor issues I have found (replacing headlights, oil change, etc) I noticed that it has the illuminated entry system, but it doesn't work. The Haynes manual I bought doesn't say anything about how to fix that. I'm going to start with a fuse, but beyond that, any ideas how to troubleshoot why it doesn't come on when the doors are locked?

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    cadillac kevin's Avatar
    cadillac kevin is offline Cadillac Owners Master
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    Quote Originally Posted by shwhitley
    Just picked up my 75 Sedan DeVille with 44K miles last week. Working on ironing out the minor issues I have found (replacing headlights, oil change, etc) I noticed that it has the illuminated entry system, but it doesn't work. The Haynes manual I bought doesn't say anything about how to fix that. I'm going to start with a fuse, but beyond that, any ideas how to troubleshoot why it doesn't come on when the doors are locked?
    You'd be far better off with a factory service manual.
    As for illuminated entry, could be the switch in the doors are broken, a bad relay, a bad fuse, or a broken wire.
    77CDV and 77CDV like this.

  4. #3
    cajutila is offline Cadillac Owners Member
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    Re: 75 Deville Illuminated Entry Troubleshooting

    The light on the exterior door handle is carried to the handle by a fiber optic cable from a bulb in the door panel by the inside door handle. Pushing the exterior 'thumb' button switches the bulb on. My guess is that this light is on the same fuse as the other 'entry' lights. The bulb is a #558. O.E. bulbs were a kind of projector bulb with a focusing lens on the tip pointing at the fiber optic cable, but all the #558 replacement bulbs I have found are regular bayonet style without the lens on the end which must work o.k. since the bulb is in a tubular type holder at the end of the fiber optic cable. Not positive, as I haven't put mine back together as yet.

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    77CDV's Avatar
    77CDV is offline Cadillac Owners Master
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    Re: 75 Deville Illuminated Entry Troubleshooting

    Quote Originally Posted by cadillac kevin View Post
    You'd be far better off with a factory service manual.
    As for illuminated entry, could be the switch in the doors are broken, a bad relay, a bad fuse, or a broken wire.
    If none of the interior lights come on when the exterior door button is depressed with the doors locked, but the interior lights do come on when the door is open and go out when the door is closed, suspect either the door handle switch or the relay. Do neither front door handle button activate the system? If yes, I'd suspect the relay, as it's unlikely both door switches would fail simultaneously.
    shwhitley and shwhitley like this.

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    shwhitley's Avatar
    shwhitley is offline Cadillac Owners Member
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    Re: 75 Deville Illuminated Entry Troubleshooting

    Quote Originally Posted by 77CDV View Post
    If none of the interior lights come on when the exterior door button is depressed with the doors locked, but the interior lights do come on when the door is open and go out when the door is closed, suspect either the door handle switch or the relay. Do neither front door handle button activate the system? If yes, I'd suspect the relay, as it's unlikely both door switches would fail simultaneously.
    yes, neither front door handle button makes it work, but the interior lights work just fine. I will check the relay!

    ----------

    Quote Originally Posted by shwhitley View Post
    yes, neither front door handle button makes it work, but the interior lights work just fine. I will check the relay!
    can someone give me a hint where the relay is?

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    Re: 75 Deville Illuminated Entry Troubleshooting

    Under the dash, over the driver's footwell. Should be with all the other relays next to the main fuse block.

  8. #7
    shwhitley's Avatar
    shwhitley is offline Cadillac Owners Member
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    Re: 75 Deville Illuminated Entry Troubleshooting

    Quote Originally Posted by 77CDV View Post
    Under the dash, over the driver's footwell. Should be with all the other relays next to the main fuse block.
    Great, Thanks!

  9. #8
    carnut is offline Cadillac Owners Master
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    Re: 75 Deville Illuminated Entry Troubleshooting

    And how do you know it has illuminated entry? The SPID sheet should list it as well as white rings around the front door lock cylinders.

  10. #9
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    bigm57ict is offline Cadillac Owners Connoisseur
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    Re: 75 Deville Illuminated Entry Troubleshooting

    I'm not sure it would have the white rings. My '79 has this option. The keyhole is illuminate by a light located just under the door button.

  11. #10
    shwhitley's Avatar
    shwhitley is offline Cadillac Owners Member
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    Re: 75 Deville Illuminated Entry Troubleshooting

    yes, it has the light under the door buttons, and it's listed on the list of options with the original paperwork I have.

  12. #11
    shwhitley's Avatar
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    Re: 75 Deville Illuminated Entry Troubleshooting

    I was never able to find the relay and replace it...one day maybe I can get it to work but thanks for the help!

  13. #12
    cajutila is offline Cadillac Owners Member
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    Red face Re: 75 Deville Illuminated Entry Troubleshooting

    I'm finally finishing up work on my '75 coupe and started hearing a "buzz" when I pushed the exterior button and no lights came on. I tracked down the buzzing to a relay behind the driver side kick panel. As far as I can determine, the door button activates a relay which turns on the fibre optic lights on the doors for a short time. Assuming the relay was bad I managed to find an "N.O.S." relay online, but it did the same buzz sound.

    The weird thing is that the function was correct for most of the time I was working on the car, turning on the interior lights whenever I pushed the door button. Then it started buzzing. Then it quit buzzing, but the fibre optic light stayed on all the time. Now it's back to the buzz. I have not found any info on trouble shooting this, even at the dealer. The techs there are too young and have not dealt with these cars.

    UPDATE: Installed the courtesy light bulbs on the doors and pillars and they did not work. What the hey? Fuse was blown! New fuse and lights work....and the I.E.S. also works as normal. My guess (hopefully better than previous guesses) is that buzzing, along with steady fibre optic light operation, indicates incorrect current to relay. BTW, I now have an extra relay ( G.M. part #1680200) if anyone needs one.

  14. #13
    carnut is offline Cadillac Owners Master
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    Re: 75 Deville Illuminated Entry Troubleshooting

    I would suspect the switch inside the door attached to the door handle. Dirty, loose? The illumination of the lock cylinder comes thru a fibre optic line from the door courtesy light. Does that work?

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