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

 

Sounds like a grounding issue. Check your wires from battery to starter and your grounds too.

 

could be bad inside the tumbler. you tach is probable getting no signal thats why its reading only volts. does it move as you drive in correspondance with the volts. maening if you are driving and you turn the lights on, do you see a slight power draw?

 

Check the alternator. Could be a bad alternator, broken alternator belt, or (less likely) the relay for the alt warning system. The indication the you are getting is showing that the alternator is not giving output (that is why the lights are as if the key is on and the enigne is not running).

Kent

 

yes, the voltage reading shows drop in voltage when headlights are on, while the engine is running.

 

But the voltage reading is at about 15V when the car is running on freeway speed. Doesn't that mean the alternator is charging?

 

15v is too high. It should be more like 13.8v. It is charging, so the belt is at least okay. You probably have a problem with the voltage regulator. You car is a '79, correct? That means that the voltage regulator is separate from the alternator. It is adjustable, but you may want to go have it checked at AutoZone some place similiar (doesn't cost anything). The voltage regulator also provides a signal for the alt warning light and tells the instrument cluster if the car is running/charging.