I have a 1979 RX-7. Having problems with the gauge cluster. Normally with the key in the "ON" position but the car not running the voltmeter on dash reads the state of the battery charge and with the car running it switches to TACH mode. The alternator does not come on but the gauge stays in the voltage mode even though the car is running. What could be possible causes and how is this fixed.

 

welcome to the board.

do you still have the warning lights and such with the key ON? if not, check the METER fuse.

on the other hand, if you're basically saying that the tach stopped working, then your trailing ignition has failed.