tachometer goes to 6 when i press the window switch
 

82 300d. the tach doesn't work. when i press the window switch to raise when the window is closed it pegs the tach. when i press the brake it bounces. i searched tachometer.

you have a Ground issue I think. Check and clean your ground points. there's some under the cluster. and a few other places. Not familuar with the 123's and 126 grounds

^^ X2


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Also, your Tach Amp might be out and it may be the reason your tach dosnt work. It's a Cylindrical thing on the Drivers side fender. may want to take it off, clean the connections. if not, replace the amp. (again I am assuming your car has this type, Others will chime in on it I'm sure)

Shame the engine doesn't boost this way too - it could be the new street racer modification!

o-to max rpm in the blink of an eye!