Tach issue

[88SXT]

Factory tach on my 88 hasn't worked since before I got the truck. There was a small screwdriver wedged in the coil connector I assumed was holding the dark green wire in, however, when I pulled the motor a few weeks ago I replaced the broken connector with some female spade terminals and the tach still doesn't work. I am now thinking either a defective gauge or a broken wire somewhere along the line.

I know it is a dark green wire with a yellow stripe but I have at least three cut green wires with yellow stripes in different shades of faded and dirty and I'm not sure which is which.

Does anyone know of a way to test the gauge itself before I pull my hair out trying to trace wires that may or may not even be original? (did I mention a previous owner thought he was an electrician and my wiring harness is full of more spliced connections than I care to count)

 

[SenorNoob]

About the only thing I can think of to test the gauge itself would be to arc the signal wire to battery power. And I'm not sure that would work.....

 

[bfiakas]

There's a one into three green with yellow strip wire juntion in your main wiring harness just behind the A/C compressor.The single wire comes from your coil and is zap welded to three other wires one being from the TFI module,one to your tach and the other you have to look up on the wiring diagrams,I cant remember the circuit.Ckeck to make sure the connection is solid,it is a weak point.Also go to your local salvage yard for used instument cluster

 

[adsm08]

About the only thing I can think of to test the gauge itself would be to arc the signal wire to battery power. And I'm not sure that would work.....

Signal wire is pulsed ground. Putting it to B+ will damage things. Putting the signal wire to ground with key on will spike the tach needle to the top of it's travel.