Generator Adjustment

[cafr11901]

The voltage on my M35A2 has started to run a little low this winter. I noticed that when I turn on the head lamps and run the heater (it's getting cold and dark around here) the voltage on the meter drops down into the yellow - almost toward the red on the meter. I hooked up a multi-meter and at rest the batteries are at about 25 volts. With the truck running, I am at about 27.1 volts. Turn on the lights and heater and I am down to 24.8.

The solution that I read about is adjusting the generator by removing the allen plug and turning whatever screw lies below. The only problem is that I removed the allen plug (a little more resistance that I expected) there is only shiny metal looking back at me. No screw head, no markings, just shiny metal. My concern is that I broke off the end of the allen plug??? Anyone who has successfully adjusted the generator have advice or a picture of what I should see? I don't want to proceed and damage my generator.

 

[M543A2]

Alternator Adjustment

Attached is a photo of the adjustment. The adjuster looks like a four pointed receiver like a Phillips screwdriver would fit. Adjust it slowly; a little can change a lot! Before doing it, I strongly suggest you make sure all of your battery cable connections are good. Bad connections can bleed power like you are seeing.
Regards Marti

 

[JasonS]

The voltage on my M35A2 has started to run a little low this winter. I noticed that when I turn on the head lamps and run the heater (it's getting cold and dark around here) the voltage on the meter drops down into the yellow - almost toward the red on the meter. I hooked up a multi-meter and at rest the batteries are at about 25 volts. With the truck running, I am at about 27.1 volts. Turn on the lights and heater and I am down to 24.8.

The solution that I read about is adjusting the generator by removing the allen plug and turning whatever screw lies below. The only problem is that I removed the allen plug (a little more resistance that I expected) there is only shiny metal looking back at me. No screw head, no markings, just shiny metal. My concern is that I broke off the end of the allen plug??? Anyone who has successfully adjusted the generator have advice or a picture of what I should see? I don't want to proceed and damage my generator.

If your system voltage is dropping under load, it seems like the problem is not adjustment of alternator voltage but rather poor connection or weak alternator.

 

[blisters13]

I guess we can also mention that the idle RPMs should be high enough (correct depends on engine model, either 650-700 or 800-850); that you don't have a slipping belt on the alternator pulley; that all the electrical connections are clean and tight, including all the grounds and connector to the voltage regulator; and that there isn't any defect in the heater blower motor circuit (not pulling more amps than supposed to). Also check the voltage of each battery at rest, charged; should be about 12.2 volts. If not, then you have one or more bad batteries.

Depending on battery temperature, the idle voltage at the batteries themselves should be about what you see; 26 volts or so in mild weather, a couple volts higher for temps below 40 degrees or so. I don't have the TM info for this, just my experience.