tach problem 1985 300d turbo
 

I have thrown everything at this problem and still can not solve it, a quick run down of what has been done:
replaced cluster
replaced overload protection relay & fuse
traced all wiring and it is "hot"
checked KLIMA and found no issues
The only thing left must be the tach sensor located on the bell housing but I have been unable to find it and I don't know what it looks like either! Any help on this would be appreciated and also any thoughts of other problems!
Thanks in advance!!!

the rpm relay,is the problem most of the time.it is left side of the wheelwell under the hood half way down.It is in front of the fuse box it is round and about 1-2 inches high.i wich i knew on how to post pictures to show you,but you will find it. Harald

The flywheel sensor produces a A/C voltage signal to the EGR computer that is under the passenger outer kick panel.

You need to see if there is 4-6V A/C from that sensor to the EGR computer!