No announcement yet.

How does one check a voltage regulator ??

  • Filter
  • Time
  • Show
Clear All
new posts

  • Electrical: How does one check a voltage regulator ??

    I have 12.75 volts coming from the generator, the new gauge shows no charge, the battery eventually goes dead as the engine is running and the engine quits.

  • #2
    I'm not an expert on the generator/regulator system but maybe I can help. You should have somewhere in the neighborhood of 14 volts coming from the generator. Rev the engine and the charge voltage should go up. Also check the voltage on the field terminal of the generator. Basically a generator takes the field field generated by the field voltage and mechanically adds energy to it that is applied to the stator field. The voltage regulator basically monitors the voltages and currents to regulates charging by controlling the voltage on the field coil.

    Do you have a repair manual? The repair manual I got for my M15A was inadequate so, under recommendations from this forum, I got a "Motors" manual and it has fairly detailed information. My Motors manual show a detailed procedure on testing a voltage regulator... I also got a manual for a different year that has more info on the commons stuff.
    1948 M15A-20 Flatbed Truck Rescue
    See rescue progress here on this blog:


    • #3
      Pull the cover from the regulator, and get a small piece of emery cloth, fold it back to back and run it thru the points on the voltage regulator and make sure they aren't stuck. Are you sure the generator is working? Have you looked at the brushes on the generator? One of them could be bad. I have seen the brush holder on the generator stick because the brush was not making good contact with the armature, and the whole thing gets hot. The Stude vendors sell kits to rebuild them. Is it a 6 or 12 volt system? Is everything grounded? Just a few thoughts.