For some reason my tachometer only reads voltage even when the engine is running, also the Gen, Add Oil, Add Coolant indicators remains "on" just like the key is on the ON position with the engine off.

Any clue?

Thanks,
Nelson

 

check alt belt.

 

I'd assume this is in your 79 GS, which only shows voltage when the engine is off right?

Sounds like a closed test circuit. When you put the engine in run but you haven't started it, all your lights should come on in test mode, and your tach should read the voltage. If everything remains on after starting you have a closed prove-out (testing circuit).

 

What is the purpose of the closed prove-out circuit? Hpw can I fix that?

Thanks,
Nelson

 

Prove out circuit is what turns on all the "idiot lights" when the car is started... they are there so that you can be sure that all the warnings work.

When the circuit has been closed, the lamps will light... so you have an electrical problem somewhere that is common to each "idiot light." If you can read wiring diagrams, I suggest looking at a schematic for the car... then you should be able to track down the switch or wire that is likely grounding and completing the circuit.