Flaky gauges - possible electrical issue - PeachParts Mercedes-Benz Forum

dwoloz · #1 08-03-2007, 06:21 PM

Gauges seem to be quite flaky for all but the water temp, that ones fine

For instance, when the turn signal is on, the fuel gauge and speedometer needle, bounce slightly with the rhythm of the turn signal.
The fuel gauge is bizarre, its readings are off the wall. While driving sometimes it will take huge swings (and this is driving on the flats). I have no real idea of how much fuel is in there. If the gas gauge is correct I'm getting terrible mileage in the range of 10mpg.
The speedometer wildly bounces at any speed under 20mph, after 20 it smooths out
The clock works sporradically but most of the time is static. Not too important to me but its another thing that doesn't work in the instrument panel

Stevo · #2 08-03-2007, 07:45 PM

A bad ground could be the cause of your problems except the speedo. Check the eng to body ground, driver side bell housing. There are two grounding points in back of the instrement cluster. You could attach another ground to the back of the cluster and see if that helps. (from one of the screws that hold the three sections togather) I had that problem a couple months ago and another ground solved my problem.

dwoloz · #3 08-03-2007, 07:51 PM

What was your preferred method of getting to the back of the cluster?

LUVMBDiesels · #4 08-03-2007, 08:30 PM

The cluster should just come out. It is friction held. The easiest way is to remove the lower dash cover and reach up behind the cluster and push it out. Just be careful of the speedo and oil lines...

dwoloz · #5 08-03-2007, 08:37 PM

I will be careful

The cluster was definitely removed before by someone less delicate than I. I think when they removed it they yanked on the speedo line and that what is causing the "bouncing" when the speed is less than 25mph. I think I recall someone saying to just lube the cable and then reinstall to fix it, is that true?

Stevo · #6 08-03-2007, 08:41 PM

remove panel above drivers knees, push the panel out from the back, theres a couple places to get your fingers in and push out. Its not held in with any fasteners just a tight fit. follow the spedo cabe down in the engine compartment and losen the bracket holding it, which will give enough room behind the cluster to let the other things go, oil pressure line, multi pin plug, and clock power. The small bulbs for GPs, seat belt and such can just be pulled out of the cluster. Replace any burned out dash lights while your in there. (test with multi meter). Be sure to use two wrenches on the oil pressure line so you dont twist it off

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Biodiesel300TD · #7 08-03-2007, 09:01 PM

For your bouncy speedo needle. Try disconnecting both ends of the speedo cable, at the cluster, and at the transmission. Then spray some lube into the cable and spin the square pin sticking out. Spin if for a while, then spray in a little more lube, adn spin again. Keeping doing this untill you see lube comming out of the other end. Then spin it some more so you don't have vast quantities of lube in the cable. Then reattach both ends and see if that helps.