What the voltage regulator does, the signs of failure, and the MSG equipment used to test it on the vehicle or on a removed alternator.
The voltage regulator keeps alternator output within set limits so on-board systems work properly and the battery charges correctly. It may be part of the brush holder module or a separate component, and it cannot be repaired once it fails.
A faulty regulator causes under- or overcharging. Possible symptoms:
- Hard starting, dim or flickering headlights
- Battery warning light on with the engine running
- White deposits on the battery terminals, or a completely dead car
These signs alone are not conclusive, so a full alternator check is needed. On the vehicle the MS016, MS015 COM or MS013 COM testers can be used; for removed alternators the MS005, MS008, MS006, MS002 and MS004 benches can also simulate load.