87' 300TD wagon Tacho/ac/idle speed controller

[confidencelodge]

Hello, This is my first, of probably many posts on this site.

I have a 300TD wagon that i purchased about a year ago. I have some slight issues with it and would like to see if anyone can help. I can do a fair amount of mechanical and tech work but i'm on here to gain some insight with this car.

My Tachometer is dead, the AC doesn't engage, and the idle control inside the hood is null.Im under the impression that all of these failures are tied to one problem. not having RPM data ,or a signal with that .

The OVP relay fuse replaced, though it was good to start with. i've also replaced the ecu with one i purchased on e-bay for not much money. I noticed when changing ECU, relays, and any item connected electronically , that it makes no difference whatsoever to the starting or running of the vehicle, It could start,and run without these boxes, with no issue. Engine runs smooth with good power ,but i'm under the impression that the turbo is not engaging either. I have no reference as my other car is quite gutless (2.0 litre om601 in a 190) (possibly related, maybe not)

Anyhow, I love this car and some pointers or direction would be nice. Id love to make this car tickity boo sooner than later.

After all this is sorted, i have a dreaded dead sunroof to repair, which i understand is not a fun party.

Thank you

[winmutt]

Was the OVP fuse blown? Probably need to replace the whole OVP, after that put on your safari hat and good hunting in the ETM! Checking tach pickup is pretty easy. There is a connector on the firewall IIRC, with engine running should be about 4v AC. No AC engagement makes me think the AC relay is shot, which I believe this all runs through as well.