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

Tiny
SENSEIANDE
  • MEMBER
  • 1985 CADILLAC DEVILLE
  • 68,500 MILES
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
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Thursday, August 2nd, 2012 AT 6:45 PM

6 Replies

Tiny
DOCFIXIT
  • MECHANIC
  • 18,828 POSTS
Suspect fault in Automatic Twilight Sentinal
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Thursday, August 2nd, 2012 AT 7:58 PM
Tiny
CADIEMAN
  • 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.
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Friday, August 3rd, 2012 AT 4:51 AM
Tiny
SENSEIANDE
  • MEMBER
  • 6 POSTS
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?

Thanks
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Tuesday, August 14th, 2012 AT 7:44 PM
Tiny
SENSEIANDE
  • MEMBER
  • 6 POSTS
Oh, I forgot.
The battery was just charged and had a full charge.
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Tuesday, August 14th, 2012 AT 7:45 PM
Tiny
CADIEMAN
  • MECHANIC
  • 3,544 POSTS
Check all the fuses. What was the battery voltage at the battery when it quit?
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Thursday, August 16th, 2012 AT 3:57 AM
Tiny
SENSEIANDE
  • MEMBER
  • 6 POSTS
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.
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Thursday, August 16th, 2012 AT 4:32 AM

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