alternator issue?

[Scott]

cpl 1975 with cummins alternator 105 amp(?) alternator feeding group 31 start battery only.
Used to have belt squeal at startup and finally unhooked the air heater a few weeks ok. Ran great, no squeals until today.

started the engine, no squeal at idle but over 1000 belt squeals and gets worse with more rpm. Volt gauge at dash shows 12.0 volts even at 1500 rpm when it would normally increase to 3.5 +/-. Noticed coolant cap loose and rattling, tightened. Pulled belt, visual ok but not much light. All pulleys spin freely without noise but tensioner pulley very hot. Belts, pulley, and tensioner replaced 4 years ago when I Athenized the engine.

Where do I start trouble shooting this? I have read that I can remove the field wire from the alternator to see if that is the issue- what is a field wire and how do I identify?

Topic

[Rob Schepis]

The field (exciter) is #1 on the 19SI and is basically the ON/OFF control from switched 12V.

If the alternator output is not there even as RPM’s are introduced I do not believe the field wire is your culprit.

Belt squealing over 1,000 rpms ?? That needs to be sorted out ASAP.

Probably best to get that alternator out and to a good shop.

Have some good pictures of the the alternator and the front engine (with the belt guard off) so we can see what you are seeing?

How many engine hours?

Engines under a salon or under a leaky deck?

[Author]

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