The temperature gauge on my W126 300SD had become erratic. I'd fixed every other instrument in the cluster but shortly after this dumb thing went on the fritz. Either it would plain flat out not work at all or it would bounce around in a very jerky manner between zero and a normal reading.

It's the sender of course. You can find it between the block and the injection pump; it's a black plastic thing that clips on to the side of the block. You pull it off by pulling away from the block. This will expose a brass pin in the side of the block and you'll have a connector on a wire in your hand. Or in my case a connector AND a wire, two separate things. No wonder my gauge didn't work.

Using a very small (jewellers) screwdriver, carefull pry open the black plastic connector which will expose one of the ubiquitous silver plated Mercedes barrel connectors. Clean the heck out of it (I use a Q-Tip which JUST fits inside the connector) and resolder the wire if yours broke off too - and if your gauge is dead I'll bet it did - then put the connector back in the plastic houseing, snap it shut, put it back on the pin sticking out of the block and I'll betcha your temperature gauge will work now.

Richard Sexton
Aug 22, 2003