Testing Voltage Regulators
If you have a charging problem, you may want to find out if the VR (Voltage Regulator) is the problem. A faulty VR can cause various problems, the most common are no charging or too high a voltage during charging. NOTE that the stock factory VR internal setting is such that the battery terminal voltage is typically 13.8 volts during cruising (the higher voltage Authorities...Police...regulators are about 14.2). The 13.8v is a reasonable compromise for water use on flooded fillable batteries, but really too low for best battery life, particularly on AGM/VRLA batteries. There are TWO very easy ways to test a voltage regulator that do NOT involve the technical methods in the rest of this article. These two methods are: 1. Substituting a known good voltage regulator (any 1970+ BMW airhead regulator, or any three terminal automotive regulator that fits the airhead plug). If whatever the problem was now disappears, then the VR was faulty.