##!! tach is doing it to me again.
 

Okay, so tried the "filter" trick, then did a more permanent solution, by taking the sending unit apart and looking for any cold solder joints or loose connections, found none, but touched up some areas anyways and checked for cracks in the circuit. Determined that it was not making a good connection because the pins were loose, so was able to tighten everything up with some black silicone windshield adheasive... Worked great, problem solved.... for two 1/2 weeks. Now my tach is working when it feels like it....kind of like my son keeping his room clean... then today my tach was jumping all over the place to the sound of a relay? coming from the far right glovebox area.... decided to work for 10 minutes, now it's on break. I give up... anyone have an idea what's going on? Out of curosity how many model years were affected with the tach problems? Mine is the '80 300sd.

Thanks in advance!

Les

Mine used to do that, where it would bounce around all crazy, then it died, and has never moved since, not even once...and that was a year ago. I replaced the gauge, and the amplifier, no go. I have no idea. Eventually I'll look into the sensor and other things once its warmer out, as its 12 degrees right now...

could be a sensor-mine works but reads too low & end of sensor is broken off.

My guess is it is that RPM sensor. I've fooled with it plenty and have basically given up, which I rarely do. I'm too damn cheap to buy a new RPM sensor for now.

The sensor huh? Is there no end in sight? I guess I shouldn't complain it is a 25 year old car... but dang, all these little things are happening on my shift. Will be added to my growing list of things to do. So where might I find the sensor on my engine?

Thanks again!

Les