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Old 11-04-2002, 04:37 PM
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96C220 96C220 is offline
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Join Date: May 2001
Location: Hamilton, NJ
Posts: 367
W126 420 SEL Dome light diagnosis help...

Ok, spent a few mins toying with the SEL again...

Here is my problem. When you open the drivers door, no dome light comes on.

When you open passenger door, or either rear door it works fine.

I immediately suspected the door contact switch, so I swapped passenger and driver side in the front (assuming that if it was the switch, the problem should alternate sides) , and the light system did exactly the same thing.

Passenger side lights up, drivers side doesnt.

I know that the drivers side door contact switch goes through the seat belt warning / headlight warning "buzzer" but that works fine.

Next thing im thinking is there is a bad ground to the contact switch.

One side should show ground constantly, and the other side should not, unless the circuit is completed. Is this correct?

Also, there are two sides to the contact switch, one that has a shielded terminal (in some sort of plastic sleeve) and one that has an exposed terminal.

Anyone know off hand which one is supposed to be constant ground?

Any other ideas of what might be causing this?

Thanks again.

George - new e-mail

1996 C220 - 109k miles
1989 420 SEL - 243k miles
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