K, here it is again. I post this about once a year to see if anyone has any new insight, as this is a recurring problem on a few of our cars and no one has found a fix (at least as far as I know).

My tachometer only seems to work when the car is first started in the day, and ONLY when it is cool outside. The rest of the time, or after the car is riven a mile or so, the tach needle slooooowly starts to creep up. Very slowly. So in the matter or 45min, it is red lining. It doesn't respond at all to any engine inputs, it just creeps on its own.

Any ideas? I've pulled the guages out for a number of other reasons, and each time inspected the tach unit on the guage cluster. Can't find anything wrong! Needle swings freely (no binding), and a multi-meter on the thing shows nothing I can determine as bad. The car itself runs great, so I can't imagine its a bad ECU. Doesn anyone know where the tach gets its info from? Is it from the ECU, or is it from another sending unit somewhere on the engine?

Any ideas? Anyone else with this problem? I'm clueless. Thanks for the help.

Mike

 

I would get another gauge cluster from a salvage yard or Ebay for around $50 or so. You could even get a SE instead of your GLE black faced one you have now. If It still does the same thing resell it.

 

You could try putting a multimeter on the tach wire leaving the ecu. I'm not sure whether or not it would actually go directly tack but that would be a start. The tach wire's signal is in AC volts. Otherwise I'd just buy a used speedo cluster and yank the tach out of it and put it yours (assuming each dial comes out seperatley). I did this with my old car when I broke my fuel gauge needle in the attempt of installing custom gauges.