Headlights go on even when the switch is in the off position

1985 CADILLAC DEVILLE
68,500 MILES
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SENSEIANDE
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  • 6 POSTS
When I turn the key to the on position the headlights come on even though the switch is off. After about 20 seconds I hear a click and the headlights go off. Then it may or may not repeat this process once the car is started. Once I pull the key and walk away the battery is dead the following morning even though when I pull the key the headlights are off. It is a new battery and I have already checked the alternator,battery-starter and various grounds. Is this a headlight switch problem or is there yet another module causing the issue?
It's driving me nuts ...HELP

Thank You
Aug 2, 2012 at 11:45 AM
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DOCFIXIT
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  • 18,828 POSTS
Suspect fault in Automatic Twilight Sentinal
Aug 2, 2012 at 12:58 PM
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CADIEMAN
  • ✓Experienced Mechanic
  • 3,544 POSTS
follow the clicking noise to the sent. module under the l/side of the under dash.disconnect the box.than they will work manully. u you will need to replace them to fix this.the sent. module and eye.
Aug 2, 2012 at 9:51 PM
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SENSEIANDE
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OK, I finally got around to unplugging the twilight sentinal. The headlights no longer go unless I turn them on. However, while buttoning up the under dash covers I had the radio on while the car was running. All of a sudden the radio went off and slowly all the lights and functions to dash guages (I.E. fuel data center, ac controls etc)then went out. The car was still running and then a few minutes later the car died.Upon attempting to re-satart there was no power and the car wouldn't start? That's a lot of functions to go out in a short period of time. Any ideas on this one, besides a match or a sledge hammer?

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Aug 14, 2012 at 12:44 PM
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SENSEIANDE
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oh , I forgot.
The battery was just charged and had a full charge.
Aug 14, 2012 at 12:45 PM
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CADIEMAN
  • ✓Experienced Mechanic
  • 3,544 POSTS
check all the fuses.what was the battery voltage at the battery when it quit?
Aug 15, 2012 at 8:57 PM
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SENSEIANDE
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the battery is new and was at full charge when I started the car. The car ran for less than 5 minutes before it died. The radio went first (as I was buttoning up the drivers side underdash cover,it went out then back on and then out for good) and then the ac a fuel data center faded out about a minute later. I didn't think to check the battery after the car died because of the frustration of this in 100 degree weather with severely smoke filled skies due to the local forest fires. I will check it tomorrow. I can re-jump the car with my pickup and it starts but again the same string of events happens again.I looked at some of the fuses but not all. I'll recheck them all tomorrow.
Aug 15, 2012 at 9:32 PM
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