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1968 Deville
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7 Posts
Discussion Starter #1
I have a 1968 Deville that I'm bringing back from the dead- it had been sitting for 5 years... And problem number 503 is that the high beams are stuck on. Even when I press the floor button, they don't go off. It has the auto-dimming feature too, unfortunately, which seems to twist endlessly. But isn't the floor button supposed to override that?
Is the floor switch possibly bad? It feels right, and makes a loud clicking noise...
Also, is there a high beam headlight relay that I can remove to fix the problem temporarily?

Thanks for any advice.
 

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83 Eldorado, 90 Seville, 94 Concours
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469 Posts
When the relay went bad in my 83 the high beams stuck on.
On 1979 and later equipped with the guide-o-matic auto dimming option used a dimmer relay located near the fuse block. On 67 to 78 models the option doesn’t appear in any of the elect schematics in my manuals. If you have any headlights at all indicates power thru the main switch. Check around the fuse block and see if you can find a silver box about 2”x1” it may have printed on the cover “GUIDE” and a part number. Also use a test light to check the dimmer button, just because it clicks doesn’t mean its good. Note: electrical contacts tend to corrode overtime.
The looseness in the main switch might just be the culprit in that it won’t hook-up and turn off the auto-dimmer routing the current to the floor button.
My thoughts are that there must be a relay controlling the auto dimmer. I had to scrounge my local U-Pull yard for parts. My advice, When you find auto-dimmer componits grab them.
 

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1926 Model T street rod, 2000 Jaguar XJ8, 1999 Corvette.
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6,738 Posts
All power for headlights is routed to the floor dimmer switch first, then to the guidematic then to the dash switch. The logical place to start is the floor dimmer switch. Pull back the carpet and verify power and ground to the dimmer switch. Should be 3 wires to it. Hi beam, low beam and ground. With hi beams on, you should have power to 2 wires. Low beam filiment as well as hi beam filiment, low beams will only have power to 1 wire.
 
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