Checking the voltage regulator

Connect a multimeter between the terminal «+» generator (red wire) and mass.

Let the engine run for two minutes at 3000 to 4000 rpm (diesel engine approx. 1800 to 2500 rpm) in order for the generator to warm up to operating mode (around 80°C).

Turn on the parking lights, radio or fresh air blower. This corresponds to a current load of three to seven amperes. The control voltage should now be between 13.5 and 14.8 V.

If you measure higher voltage, the regulator is faulty and should be replaced. If the voltage is too low, according to experience, graphite brushes are worn out in the generator. In this case, dismantle the generator and have it repaired in a workshop.