Aging alternator rectifier bridge? Alternators not producing 100 amperes?


Active member
Schertz TX
I'm trying to make my 1031 perfect, one thing that bothers me is the afterglow period of the glow plugs dips the voltmeter deep into the yellow so I hooked my voltmeter to the system while starting and running. Sure enough, system voltage drops into the 23 volt range when glow plugs are on and engine running. Even when well above idle speed (around 1500 RPM).

This indicates to me the alternators are not putting out full rated current since batteries are new, starter is freshly rebuilt and alternators put out 14.8 volts when cold. There is the key, when the engine warms up, alternator output drops to 14 volts and under with only mild load. When I say mild, that would be the heater blower for the front battery and a listed 10 amp fan for the back battery. I have measured as low as 13.2 volts with these loads, I would think a 10% load would not drop the voltage so much.

The -34 TM lists acceptable voltage drop to 14 volts with 90 to 100 amps of output. Guess the problem would be the rectifier bridge?
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