Mysterious Tach Wire

[nrpolo]

Trying to sort some issues on my new to me 2003 2100 sd that has a 4.3 MPI. My tach is stuck at 800 rpm weather running or off. I have cleaned the terminals at the tach and rotated the 4-6-8 switch in the back with no luck I have tried to locate the grey wire from the coil. I found a grey wire marked tach in the front of the engine that has a black rubber plug in it. There is also a disconnected ground coming from the same part of the harness. Is this set up for a remote tach when working on the engine? Does anyone know where the wire comming from the coil that goes to the gauge can be found? Thanks in advance.

[mmwjr]

The tach wire should be connected to the negative terminal on the coil and the other end on the sense terminal of the tach.

Common to have an extra negative on the wiring harnesses that is not used.

[jparsons121]

If it's stuck regardless of key position, it may need the "Faria rap".
Daria gauges are known to get sticky when they get older and will not read, move as expected. A couple of sharp raps with your knuckles with key on may rule out this condition.

[nrpolo]

I like that kind of "fix". Will give it a couple of smacks.

[The Pirate]

And if not, ship it back to Faria in CT, and they will fix it.