Alternator question on Cummins 6BTA5

[tedkuw]

I have a Cummins/Delco Remy 24SI, 12VDC, 160A alternator on Cummins 6BTA5 330HP diesel (on Nordic Tug 37). No output from alternator. Pulled it this morning and had it bench tested....test fine. Cables look OK...no rust or weak connections. Any suggestions where to look from here?

 

[High Wire]

What was the starter bank voltage? Were you anchored or at a dock? If your battery bank was fully charged when the engine was started then the alternator wouldn’t charge.

 

[tedkuw]

Alternator not charging on Cummins 6BT

Thanks for the quick reply. The boat was at its slip and batteries were fully charged. After warming up engine, I tested stern thruster that works off the house bank. The voltage went down to 10 volts; normal operation shows alternator supplying additional current and voltage remains at 12+VDC. Also, voltage at helm meter only showed 12VDC...normally, voltage shows charging voltage when motor is running.

 

[Eli27]

Do you know what excites the alternator? Pretty sure that's where your issue is. Also, check voltage at back of positive wire(the big one) against what is at the battery. If back of alternator is charging and battery is not, check for some type of fuse or do a voltage drop test.

Voltage drop test- take a digital dvom, from point of connection to point of connection on same circuit check voltage reading. Should be very very close to zero volts.

If you see a voltage of .02volts or more, check for terminal tightness and corrosion.

Hope this helps

 

[Bacchus]

Alt excite is one possibility.
Do you have some sort of isolator/ combiner that allows charging of both start. & house under the right conditions? That is another possibility.

 

[O C Diver]

Thanks for the quick reply. The boat was at its slip and batteries were fully charged. After warming up engine, I tested stern thruster that works off the house bank. The voltage went down to 10 volts; normal operation shows alternator supplying additional current and voltage remains at 12+VDC. Also, voltage at helm meter only showed 12VDC...normally, voltage shows charging voltage when motor is running.

Did you check the battery? A failing cell may limit voltage. If you have an infrared temperature gun, try checking the temperature of the alternator with the engine running to see if the alternator is heating up from charging.

Does it have an external regulator like a Balmar?

Ted