PeachParts Mercedes-Benz Forum - View Single Post - '90 300 SEL: All instruments lights go out

tinypanzer · #7 04-13-2009, 09:19 PM

One last thing regarding contact cleaners - they are not all made equal. A lot of them contain no lubricants in them, and as a result they will clean out not only the dirt contaminating your potentiometer, but also the grease lubricating it. If the knob feels all crunchy and scratchy afterwards, you'll know this has happened.

There are two ways to deal with this. The first is to actually open it up and replace the grease which got washed away by the solvent. The second is to use a contact cleaner that contains lubricants. Neither EPC nor DeOxit contain lubricants of any real viscosity.

A good compromise is to use a contact cleaner that contains silicones. You may have to use quite a bit of it before the silicones build up enough inside the potentiometer to have any effect.

Either way, make sure the pot is lubed. If it isn't, the wiper will eventually chew through the trace on the pad and you'll have to replace the whole shebang.

Wirewound pots are different. They typically do not require lubrication on anything other than the shaft. I think the dash light pot might be wirewound, based on its physical size, though I'm not 100% sure because I've never opened one up. If this is the case, then lubing it isn't as big an issue.

On second thought, the dash light pot probably isn't wirewound because wirewound pots typically don't have the issue you're having. They also 'feel' different than normal pots because you are dragging the wiper across wires and you feel the bumps......