TACHOMETER
 

The tach on my '91 420SEL stopped working. Checked for loose connections on the gauge. What sensor/sendor does this work on and where is it located. I guessing that's the problem.
Thanks, Dave

TACHOMETER
 

Blank stares. Slacked jaws. I'm hearing crickets people.
Anybody?

if its like the diesels there should be a little "trash can" looking plug on the wheel well that commonly comes loose.

check this url. www (dot) benz world (dot) org/forums/w123-e-ce-d-cd-td/1597328-w123-300td-tachometer-problem.html

i chopped up the url a little. im not sure if im supposed to post links to other sites.

On my 84 500SEL the tach signal comes from the ignition module at the left front of the engine compartment. It is called the TD signal. If the fuel pump relay doesn't see this signal, the car wont run.
I don't know but I believe the Generation 2 gas cars are the same. Also, on the Gen 2 gas cars, the A/C won't work if it doesn't see the TD signal.
Sorry I can't be more specific.

Paul

The tach signal on the later cars (I believe) is sourced from the EZL module. It is accessible at the X11 connector on the driver's fender.

Looks like its on pin 1, based on this information.
BOSCH KE3-JETRONIC MIXTURE ADJUSTMENT

If you have signal there then the problem is upstream. Could be failed capacitors in the tachometer.

It sounds like it is different from the diesels. Well, we got this thread movin'.

On my 85 500SE, I've been having trouble with the heat on all the time, then the AC stopped working, and after the shop switched out the AC regulator, the ACs working but the tach stopped working and the heat is still flowing all the time. Do you think the AC regulator swap and the tach now not working are related?

The tachometer signal does pass through the AC relay I believe. This is so that the AC relay can kick off the ac compressor at certain speeds.

Thanks, but no fuel or A/C problems.

No tach
 

Thanks all. I will check the connections at X11. And try to source a different tach.

Thanks! Appreciate the help!