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'81 CDV, '64 SDV, '73 MB 450SL
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224 Posts
Discussion Starter #1
Hi there-

We have a Seville. It's been a basically good car, but it has a strange new electrical gremlin that I can't sort out. I am an experienced tech, and specialize in electrical repair. There are no obvious issues with this car.. so I'm hoping someone here has had a similar experience and might know where I should look next.

The battery has been dead randomly in the morning for about the last two months. Most days it starts fine.

A few weeks ago, I happened to be in a room adjacent to the driveway at night and noticed the interior lights were on and off at about 10 second intervals. I hit the keyless entry lock on the remote and they stayed on a little longer, and went out, then I went to bed.

A few days later, I was headed outside to go to work, and noticed they were doing the same thing. With no time to worry about it, I jumped in my trusty diesel Benz and headed to work. When I got home, the battery was dead.

This evening, I looked out the window, and it was doing it again- on and off at 10-20 second intervals, with more on time than off time.

I know the illuminated entry system has a timer, and I guess when the lights kick on, they are staying on for the duration of the timer. I'm thinking that the illuminated entry system is to blame, as the car never does this going down the road.

I have however noticed, that on occasion, the interior lights do NOT come on when the door is opened, but after driving the vehicle, everything works fine again.

Could this be a faulty/failing BCM? I know this is kind of an early car to be multiplexed, and there are no body codes except one for 'twilight sentinal pot circuit' which should not affect the interior lights, and is left off anyway.

Any ideas would be appreciated.

Aaron
 

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98 DeVille, 97 DeVille d'Elegance
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7,345 Posts
Twilight sensor is also used to determine if/when interior lights should be turned on, regardless of where the switch is. At least the 97-99's are I know.
 

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'81 CDV, '64 SDV, '73 MB 450SL
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224 Posts
Discussion Starter #3
Yeah, looking at the FSM, the twilight sensor is used to determine when the lights are allowed to be on, ie, the courtesy lights won't work for any reason in bright daylight, and once it begins to get darker, they will work.

The sensor doesn't turn them on and off though. I think the problem is going to be a faulty door button switch. The buttons on the exterior door handles activate the illuminated entry. I'm betting one is shorted out. I'm going to cut that wire at the BCM and see if the problem goes away.
 

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93 Cadillac Eldorado ETC
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5 Posts
Did you ever find out what the problem was and more importantly the solution to the possessed interior lights on then off on a delay. I have a 93 Eldo doing the same thing. Finally took out the relay to stop battery drainage.
 
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