Have replaced alternator, voltage regulator, and battery twice! Still having problems with over charging. Anyone have an answer?

 

Assuming you still have an external voltage regulator this is my best guess:

https://www.dieseltruckresource.com/...solved-317745/

If the reference voltage to the regulator is low due to voltage drop through the aging wiring and connectors the regulator tells the alternator to charge the battery. This thread addresses pulsing but if the drop is enough it can charge continuously.

Good luck,
BlueW250

 

Just had the same issue with the reference voltage on my black '85 crew cab that uses a '91.0 wiring harness. I had voltage that was running high and bouncing.
Re wiring the signal to the VR fixed my issue.

 

Interesting, I have just lived with the pulsing for only about 19 years or so. The other thing is that is the same relay that I used to excise the problematic KLIMA relay on my '86 Mercedes 300 SDL . It is wired into the AC system and monitors 7 or 8 different sensors that all can shut down the AC system, a real PITA. I really like things as they were made at the factory, especially on classic or collector cars but trouble shot until my eyes were bleeding even though I had already found the relay fix. About 8 bucks and 10 minutes after I got the relay, the problem was solved, no KLIMA and cold air . For me, the really cool thig is there are no permanent modification and if someone wants, the KLIMA can be replaced...Mark