Hoping someone can shed some light on a dead tachometer on my "new" 1987 300 SDL. What's the most likely cause?

The only other problem I have is an ABS sensor. I cleaned both front sensors and the light remains on. Hopefully, after I do the rear sensor that problem may clear.

How many of these cars do you find with less than 100K on them? I must have been pretty fortunate. MPG seems good. I drove it 500 miles to get it home and got 29 using cruise. I was pleased with that.

Wow it has less than 100k? Thats a pretty impressive find! The vast majority of these cars are in the upper 100k range to mid to upper 200k range.

Not sure on the tach on an SDL....it might be the sender....or it could be a bad ground.....others will chime in I'm sure.

Also not sure on the ABS, perhaps a bad wire to the sensor?

__________________
-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

Does the idle seem low after starting and the idle adjustment doing nothing? If so I would pop the hood the next time you start it and look for the Over Voltage Protection (OVP) Relay. It is located a little to left of the steering wheel in the very back of the engine compartment with a red top and about 1" square. Pull back the plastic cover and give it a good tap or two with a wrench or something. Fix my problems about a month or two and haven't had any since. Good luck.

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1987 300SDL-268k mi

After reading this post, I decided to check mine. (OVP) My tach would work randomly once in a while so I thought bad connection. I found the ovp , and took out the fuse. The fuse is only "half blown. It has a small bridge between the points. Maybe thats why it worked sometimes? I have not gotten a new fuse in it yet, but I think it will work.

This forum is great

I just tried the new fuse, and nothing. I think my outside temp sensor works now. Is there any thing else I should check?

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Dave

1985 190D 2.2 auto--gone
1975 240D 4-speed--storage
1985 500SEL--daily driver
1985 300TD--bad rust, soon to part out...
1982 300SD--waiting on engine from RD
1984 190E--storage
1996 Dodge 2500 Cummins--daily driver

Yes, my 87 SDL still has less than 100K. A few hundred more miles and it turns over. No luck on the tach yet. I tapped on the red relay to no avail.
I'll have to wait until I can get someone to sit behind the wheel.

Anyone who knows what "drives" the tach please let me know. I would have thought there is a relay that controls it but I'm just in the process of trying to accumulate reference materials on the 124/126 cars. Just got a 123 ref cd on the 123 cars and that doesn't even work.

Thanks again and have a nice long weekend everyone!

dave

If the cruise works, it's not a flywheel sender or OVP relay problem.

Pull the gauge cluster and make sure everything is connected. I'm pretty sure the tach signal comes through a green wire with yellow stripe in one of the two pin connectors directly behind the tach. The flywheel signal goes into the EDS box then splits to the X11 test connector, Klima relay, tach and cruise control unit.

To test the EDS rpm input, change the setting of at the rotary knob under the hood by the fusebox. Note the current position. Pull up on the knob, turn and push back in at another number setting. This should adjust idle by 50rpm up for higher numbers or down for lower numbers. If that works, the EDS is getting an engine rpm signal.

I know quite a bit about where things are in an SDL but I have no idea where the EDS box is

Sixto
87 300D

The OVP relay fails some times, with the fuse still good.

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Gone to the dark side

- Jeff