Technical Ammeter pulses between 0 and + 15, what's wrong?

Brought a late '6os Ford out of a 13 year hibernation. The ammeter rhythmically pulses from 0 to +15 amps. The instrument lights pulse with it. It has a Ford alternator with external regulator. The alternator and regulator were less than a year old and working fine before the long sleep. Any ideas on what's happening or fixes?

 

Load it up with heads lights and all the other electrical. I think if it stills pulses you have either a regulator problem are a diode in the alt. IMHO

 

bad ground

 

sounds more like a bad diode trio in the alternator ( they die unexpectedly ) , if not the instrument panel lights power regulator ( ford has this in the dash )

also the contacts on the voltage regulator might be dirty and causing it to act up too . lots of things corrode and break while in long hibernations .. pull the VR cover and do a quick reset on it .

 

What bedwards said. Bad ground between engine and body on the last one I had that issue with.

Len

 

Another vote for bad ground