Could anyone give me some suggestions about my tachometer on my 83 300D which i just bought. Most of the time it dosent work, or it may work sometimes esp. if left at idle for a while. Sometimes the needle jumps around. Where should i start? Replacing the gauge or is it something else?
Thanks,
Jeepboyosu

Do a search on it you will find lots of info on this little gremlin. (search link towards top right)

The tach works off an rpm sensor on the front of the motor. The sensor very seldom goes bad. The AC signal generated by the sensor is interpreted and converted to a pulsed DC signal by a transducer screwed into the diagnostic port on the left fender. This is almost allways the problem and isn't very fixable without replacement as the electronics are sealed in plastic (molded in plastic).

The pulsed signal goes to the tach which is fairly trouble free. From fixing many bad ones I can verify their failures though. The failures are almost always the capacitors in the tach circuitry.