ajmiceli22

I recently bought a 78 silver anniversary with an electrical short. The previous owner installed a simple knife switch on the positive side of the battery so the short doesn't drain the battery when not running. I replaced the old battery with a new one. Now at idle the voltage tac reads a little high but when I accelerate the voltage tac goes into the red and there is major static when the radio is on. When i come off the accelerator static clears but voltage tac still reads very high.
Could I have a bad ground somewhere? or a bad alternator?
Any advice would be helpful. I don't know where to begin looking for the problem
Thanks

lionelhutz

Put a voltmeter between the case and output stud of the alternator. If that doesn't read around 14V with the car running then take the alternator off and get it tested.

Honestly, there really is no way to get a high voltage unless the alternator is bad. Basically, the regulator has gone bad and is stuck full-on all the time.

Don't keep driving it like it is because it'll just kill anything electronic and blow light bulbs.

ajmiceli22

Thanks I'll start there.

The13Bats

When my 69 first got here and I got it running ( modded, non bubba car ) it had a short that would drain the battery fast, I found it when I placed a hand on the non working wiper motor it was hot as hell..disconnected it and the battery didn't drain.

Then one day I was driving early even and thought damnnit man am I having an optical migraine, the dash , headlights etc got bright as hell and the amp gauge was whacking out...in my case like the other fellow said my alt had gone bad...I got lucky didn't toast anything.

mikem350

A bad regulator (inside the alternator) can cause a constant drain

SIXFOOTER

The light delay timer is a famous fault that kills batteries

lionelhutz

A shorted regulator would explain both the battery drain and the voltage fluctuating with rpm so I'd start there before checking other things.

ajmiceli22

thanks for the help. Tested the battery was reading 18 volt while running. pulled out the old alternator and replaced with a new one, retested and now working perfectly 14 volts. I appreciate all the info