Location of Tach Amp on w123?
 

Hi Folks-

After searching and reading through instructions for replacing/repairing the tach amp, I realized that it's for w126s.

I have a w123 1984 300D, and the tachometer doesn't move. I don't see a tach amp where it's supposed to be on other cars, or anywhere else for that matter. Does anyone know where I can find it?

Thanks!

It's a round black cylinder mounted under the hood on the driver's side fender, near the front. Almost right above the glow plug relay, if you know where that is.

sometimes its a lightish brown. thats how it is on mine. heres a pic

Because your car is a 1984, it does not have the tachometer amplifier. I found this out the reverse way because I picked up a tach from a 84 300D to retrofit to my 240D. I was discussing this with my friend who is a Service Tech at Wilsonville Mercedes and he said that the 1984 and 1985 300D's got their tach signal from an EGR related item...of which I can not exactly remember. So your car will not have the traditional round amplifier.

Right, which is why I didn't see it where other posts indicated it might be.

Anyone know where the tach gets its signal from on an 84 300d? The online shop manual seems to be missing that information.

Also, from what I could find on the shop manual, the cruise control gets some of its input from the tach. Well, my tach doesn't work, but my cruise control works well. What's the deal with that?

Thanks!

The cruise control gets its input from the speedometer. The tach in the 84/85 diesels use a magnetic pickup, the signal from that drives a module located behind the glove box, it has a large (12 pin?) rectangular plug connected to it, that is called the EGR module,
DDH