D+ terminal, exite alternator?

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D+ terminal, exite alternator?

We have a dual alternator in a coach, 24V, Vanhool, 1277640, AL172RA. I am told D+ terminal in needed to turn on alternator. Both alternators have failed?? We show 24 volts at B+, B- whether engine is running or not. I am told the D+ wire used for a dash indicator but needed to exite? This wire has 17 volts which comes through a resistor and when it is hookup to the D+ it should then read only 2 or 3 volts. Do we need this wire to turn on alternator? Although we are showing 24V at main alternator cables, I have no way to load test them, but thought I should show something happening on a volt meter running verses not. We had a local shop spin one of the alternators on test stand with no output either. I don't understand why both alternators have failed. We just finished some engine work and didn't mess with any of the wiring in coach.

Prestolite Electric
Arcade, NY USA
Posts - 1204

Yes, the D+ needs to be connected in order for the alternator to operate.

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