The role of the voltage regulator in keeping alternator output within limits, typical failure symptoms and professional testing with the MSG MS012 COM.
The voltage regulator keeps alternator output within the permitted range as engine speed changes, protecting the battery and on-board electrical system from overvoltage. Whether built into the brush holder or mounted separately, it is a non-serviceable part that is replaced when it fails.
A faulty regulator usually shows up as undercharging or overcharging of the battery:
- Hard starting and a starter that cannot turn the crankshaft
- A completely drained vehicle
- Boiling electrolyte and white deposits on the terminals when overcharged
Symptoms alone are not conclusive, so the regulator should be tested with equipment together with the other alternator circuits. The MSG Equipment MS012 COM tester checks 12 V and 24 V regulators under different loads for fast, accurate results.