Trouble with Voltage Regulator(12 volts) on GMPD4106

[Fred Mc]

Today I started the bus (12 volt system) after sitting for a few months and it was charging 18-19 Volts. I had replaced the voltage regulator with an electronics replacement board from Luke a couple of years ago and its worked fine. I was able to adjust the voltage with a "pot" on the regulator board to 13.8 but that is as far as it will go. (It just occurred to me that 13.8 may be the battery voltage and the alternator is turned off).
At any rate any ideas on WHY the voltage would spike like that.

I know some have added a belt driven alternator and a voltage regulator(sometimes built into the alternator). Is it possible to just add an "over the counter" voltage regulator to use with  the
existing gear driven alternator. With the current setup in addition to the regulator there is also a long tube like "thingy" (sorry for the poor description but its been a couple of years since I changed the regulator and this "thingy" is  hidden behind a wall in the bay.

I'm trying to get ready to go camping should the border miraculously open next month.

[richard5933]

According to the manual, with a full dummy load attached the output of the should be 13.7 volts. If you're seeing 13.8v, then perhaps things are okay.

[Fred Mc]

I understand its fine now.I guess I'm wondering WHAT would cause it to spike so high,You don't have to run it long at 18 volts to ruin your  batteries.

[richard5933]

I'd check all the relevant connections. Perhaps it was not reading the battery voltage correctly due to a loose/dirty connection and kept cranking up the voltage trying to compensate.

[luvrbus]

A open ground causes a voltage spike on GM buses those regulators are bad about that