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Overhauling a W126 Front Interior Light


Overhauling a W126 Front Interior Light

Now, first off I have to say I havn't actually successfully done this. What I did do was take mine apart, breaking it in the process, then cursing mightily when I realized how simple it was to take it apart properly. Had I done this I would probably have been able to repair my defective one - the time delay circuit had failed causing a short that caused fuse 15 to blow - the one that controls all the interior lights.

Now, my time delay circuit board is in three pieces. I broke it taking it apart, but the life it sacrificed was not in vain; I now know how to take these factory-proclaimed-not-serviceable modules apart and fix them.

The one catch is you have to unsolder the circuit board from the 4 spade connectors you unplugged the wires from. Once you've done that properly you can pull up on the two copper contacts that fit into the plastic body and the whole circuit board - and it's not much bigger than a large postage stamp - will come free.

Don't mess with the switch part. I did and could not for the life of me get it working again - it's not a big rubust thing like the seat switches, it seems to be pretty flimsy actually.

Now that you have the circuit board out you need to test it. It's mostly resisters; there's a capaciter, a solid state relay and a 1455 timer chip, but that's it. In my case the relays was fried and shorted 12V to ground. Nice. So, If I'd been a bit more careful taking it apart I'd be replacing a $2 part right now instead of having to get a hole new unit.

Well, as they say on eBay "my loss is your gain". Maybe you can fix yours now if/when it fails.

Richard Sexton