79 Electrical Problem

[jnenni]

I hope someone can help with this strange problem. Smoke came up from the tachometer. There is a resistor on the tach board that is burned. I am replacing the board. Now I get no electricity to the car. It started once, but will not start again. I probe at the accessory fuse and there is 12.6 volts with the key off, but when I turn it to the on position, the voltage drops to zero. The voltage at the battery remains at 12.6. Once in a while when I turn the key on, the heater fan comes on, but after a short time it goes off and I lose all voltage at the fuse panel again.

Any thoughts?

 

[I_R_DA_ONE]

I don't have a tech. manual,,, but it sounds like you may have an electrical short to ground some where.... this should be checked with no power on the system because the wiring harness may ketch on fire causing your vette to go up in smoke....
the first thing to do is disconect the battery....
Next check your positive lead that is on the battery cable to ground with switch off...should read very high on a volt/ohm meter [in the ohm position]
Next turn ign. switch on, the volt/ohm meter should still read very high with everything turned off and the coil disconnected.....but not as high as before..
If the meter reads low,,, unplug the insturment cluster and read it again...[the meter] this is just a starting point let us know what you find from here...
Mike

 

[jnenni]

Thanks for the reply. I was checking the connection at the starter where the fusible links are. It looks corroded. I turned the key to the on position to check the voltage there and when I was moving the wires around the heater fan came on and I had power again. I will clean and re-connect that connection. I then measured the voltage at the fuse panel and read 12.3 volts. I then started the car and I get 16.7 volts there. I think this is too high. Maybe thats what smoked the tach board. I am going to pull the alternator/regulator and take it to be tested tomorrow. I will let you know how it comes out.

 

[I_R_DA_ONE]

sounds like you found your problem......the alt. with no load may read high....do have them check it out..