Alternator voltage test

Connect a voltmeter between the positive and negative poles of the battery Start the engine. When starting the engine, the voltage may drop to 8 V (at outside air temperature +20°С).

Raise the engine speed to 2000 rpm. In this case, the generator voltage for a gasoline engine should be 13.5-15 V, for a diesel engine - 13.8-14.8 V. This is an indicator that the generator and voltage regulator are working normally. Generator voltage (onboard voltage) must be higher than the battery voltage to allow the battery to be charged while driving.

Check voltage stability. To do this, turn on the high beam and take measurements at 2000 rpm of the engine. The measured voltage should not exceed the previously measured voltage by more than 0.4 V.

If the voltage is higher than the set value, have the generator checked by a specialist workshop.