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ok! After fixing a couple burnt ground wires after the jumping debacle, I found some more problems. Got a new tach and clock. They didn’t work when I installed them. Checked voltages and they’re good. But when I plug them in no workey!!!;also installed speedometer from donor cluster. It doesn’t work either. Any suggestions would be appreciated!!!
Check the circuit board where the wiring plugs in. The copper can be corroded and it also can come loose from the clear plastic and get wrinkled. A little super glue to glue it back on the plastic works for me. Take your speedo head out and put it in the other cluster.
You could check continuity of the four circuit board ribbons that support the tach.
You could clean the tach per the thread in the Stickies.
Hopefully you didn’t get a bum tach, but they’re going on forty years old.
Checked clock with another power source and it works fine. Forgot to mention that both clock and tach are not original to the truck. I wired in both. So now I guess I’m going to re-wire both from scratch and go from there
I don't know if the tach uses straight 12 volts or if the IVR regulates voltage to it, but if it uses straight 12V, I wonder if you could remove it from the cluster and wire it to the coil for testing purposes?
I don't know if the tach uses straight 12 volts or if the IVR regulates voltage to it, but if it uses straight 12V, I wonder if you could remove it from the cluster and wire it to the coil for testing purposes?
Yes. I have tested tachs with the hood open. On the back of the factory tachometer, connect 12v to "B", green wire on coil [-] to "C" and a ground wire to "G" if six cylinder and also to "8" if a V8.
Finally after many days and short hours, I got everything to work! I just went back and re-did all the previous grounds I had used. Cleaned up everything behind the dash instead of the rats nest that was there. Also found out that I will need to start hunting for a new printed circuit board(plastic) without the tach wiring. Undid the main molex plug so many times it pulled the copper off two spaces where it plugs in. I have a couple of the circuits that have the tach etched on it, but my tach is hard wired. Not sure if I could use one of those board because I tried once before and it didn't work the tach. Not sure if it would double feed the battery connection on my tach. Thanks to everyone that chimed in with suggestions!!!!!!!!!!!!
If you have a 1980, they can be a little oddball in the wiring department. I m not sure the tach cluster is plug and play like it is in the little bit later models.