Originally Posted by
onehundred80
The 'N' module senses the bulb out condition.
From a MB site
'That was the cheap one. Far more expensive is replacement of the bulb warning module (it is not a relay). It is the largest item in the fuse box and is part number 126 542 01 32. Most if not all, W126 and W124 cars and perhaps others, use this same module. See if you can borrow one just to try it before you spend $$$ on a replacement. MSRP is $210. They are available aftermarket new and rebuilt for less.'
Just looking at the exterior of a few of these (your part number 126 542 01 32), I found this (
126 542 01 32 - Lamp Control Module - Album on Imgur ). Other than that I have no idea how it (the circuit) is designed/works, it looks wildly complicated and not something I would want to 'reverse engineer.