eyeteeth wrote:
In the long list of an RV updates/repairs I've been too lazy (or busy) to write, I recently had to replace mine. Opposite problem however... I was getting 18v to the battery.
However... many years back I had a similar problem, and replacing the voltage regulator was the solution. Driving home one evening and my head lights just kept getting dimmer and dimmer. With the engine running, you should get around 14.5v to the battery. Anything above that or below 12.5 warrants replacement of the voltage regulator.
A good, correct description of regulator problems.
Regulators work by sensing the amount of voltage in the electrical system and turning on the alternator's field when the voltage drops below a certain point. (The cut-in voltage varies from manufacturer to manufacturer so check the specifications before replacing a regulator if the system voltage is below 12.5v while the engine is running.) In turn, they turn off the field when the voltage rises to a certain point, usually around 14.5-14.7 volts.
Usually, regulators don't turn on the alternator's field when they fail. In rare cases, such as your 18v example, they fail to turn off the field when they should. The result in the rare cases is an overcharged battery, possibly leading to the electrolyte boiling away.
As with ballast resistors, carrying a (known good) spare regulator is easy-to-change, inexpensive insurance against getting stranded.
