rpm gauge quit working
 

Tach does not work. wondering if it is in the wirenes harness
or the sensor itself. Are there any way of checking the wirenes harness
to see if it is defective or the sensor itself.

Hi Larry welcome to the forum - it would help your post if you stated on which car you have a problem.

Are all other accessories (clock,raido..etc)working? I would look at your fusebox first.
My tach went out the other day, and it was that , While I was at it , I replaced all the fuses... They are pretty flimsy ... css190e 91 2.6 gas .. hope it helps

RPM GAUGE QUIT WORKING
 

SORRY ABOUT NOT POSTING WHAT AUTOMOBILE THE TACH QUIT WORKING ON. IT IS A 1995 MERCEDES 300E DIESEL. I WOULD LIKE TO KNOW HOW TO TROUBLESHOOT IF THE PROBLEM IS WITH THE WIRING OR THE SENSOR ITSELF? SOMETIMES THE TACH WILL WORK IF THE ENGINE IS RIVING UP ABOUT 2500-3000 RPM THEN IMMEDIATELY IT DROPS BACK TO ZERO. I HAVE CHECKED THE FUSES AND FOUND NO TROUBLE WITH THEM. IN FACT I DO NOT THINK THE TACH IS FUSED, IF SO, I CANNOT FIND IT.
THANKS!
LARRY L L

If I were you I'd clean all of the electrical contacts first and see if that helps. Do the easy and cheap first! It won't be a fuse problem - as in a blown fuse - if it works intermittently. You might need to clean up the contacts on the fuse though...

The tach gets its signal from an electronics box that operates the EGR system (and other things). This box is powered through an over-voltage protection relay, which has a ten-amp fuse. While you are checking for bad contacts and connectors, check the OVP (probably in a little compartment behind the battery).

Since you have a diesel, you may wish to post in the Diesel Discussion -- the diesel experts hang out there. Your 1995 is the last year for the W124 chassis and the first year for the OM606NA engine so it is somewhat unique.

Please don't write in capital letters; it is the Internet equivalent of shouting and some people consider it rude and won't help you with your problem.

Jeremy

RPM gauge quit working
 

I cleaned the contacts on the fuses and it did not help my problem. It did
help my windshield wiper work continious on intermitten. Thanks!
Jeremy thanks for the information. And thanks again for reminding me to not write in capital letters. I haven't heard this before so it is all new to me. I will make sure from now on that I do not write in capital letters.
The wiring harness goes from the sensor down to the fly wheel cover and
with a small bolt it looks through a hole in the fly wheel cover. Just wondering if there is a magnet on the fly wheel and the piece of copper on the end of the wiring harness picks up a small amount of signal and sends it to the sensor. If so I would think it would be less than voltage.
maybe something like millivolts (sp).