My '87 5.0 LX has been parked in the garage since 1999. My son is almost ready to get his permit. We have it almost ready to go back on the road, but the tach does not work anymore. I have cleaned the pins, checked continuity on the instrument cluster traces, checked that it is getting power, checked the signal @ the connector with a test light, it gets brighter as the revs are brought up.
I imagine the tach itself is toast. I have not done any board level troubleshooting in decades. I checked point to point for continuity on the board, also none of the resistors read open.