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Old 01-02-2020, 03:45 PM   #1
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Alternator issues Cummins qsa 5.9

Seeking advice, had an alternator fail (Delco Remy) 19si. Replaced with new unit equivalent 105 amp. After 15 minutes operation alternator no longer charging.
Just recently had bow and stern thruster installed as need to take vessel through a lock to enter our marina berth. Bow thruster is wired to the start batteries (2xn200 endurant 1100cca less than two years old), voltage drop on gauge when using thruster drops to 10 volts but recover ps quickly once off.
Could the thrusters be impacting the alternator?
Have checked there is power to alternator.
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Old 01-02-2020, 04:04 PM   #2
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Quote:
Originally Posted by Prelude View Post
Seeking advice, had an alternator fail (Delco Remy) 19si. Replaced with new unit equivalent 105 amp. After 15 minutes operation alternator no longer charging.
Just recently had bow and stern thruster installed as need to take vessel through a lock to enter our marina berth. Bow thruster is wired to the start batteries (2xn200 endurant 1100cca less than two years old), voltage drop on gauge when using thruster drops to 10 volts but recover ps quickly once off.
Could the thrusters be impacting the alternator?
Have checked there is power to alternator.
How do you know the alternator is not charging after 15 minutes? What do you see? What is the actual start battery terminal voltage not what the dash gauge says?
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Old 01-02-2020, 04:24 PM   #3
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Voltage on gauge and smart craft digital dropped from 13.7v to 12.4. Terminal voltage at alternator was 12.6 v when I checked with meter.
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Old 01-02-2020, 07:35 PM   #4
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If you measure battery voltage at the alternator when the engine is off and the voltage does not go above 13V at 1200 rpm, your alternator is likely toast. Get it replaced. Infant mortality on these China specials can be high.

You probably know this but make sure you do not turn off the battery switch while the engine is running. This will blow the diodes in the alternator.
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Old 01-06-2020, 06:09 PM   #5
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Thruster use can hammer an alternator if engine is running. Especially a cheapo alternator. Volts down to 10 cause it to go to full rated output and if diodes or regulator are weak, either can burn out. Worse if engine revs are up.

For this (and other reasons) I don't like connecting thrusters to other batt banks. Much prefer the thrusters to have stand alone batts located right next to thruster.

Any warranty on the alternator?
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Old 01-06-2020, 08:08 PM   #6
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I know where Ski is coming from with his recommendations above. Yes the windlass load probably did your alternator in. Also he has some good suggestions about putting a separate battery up in the bow dedicated to the windlass. It minimizes voltage drop problems and putting a heavy load on the other systems.

But you do need to provide for a way to charge that forward battery and isolate it from the starting battery so it won't leave you stranded. A battery combiner or ACR is one way. See How to add a remote battery bank on a boat.

But if you do have adequate wire size up to the windlass then upgrading your alternator could be cheaper. The Delco 21SI should be a drop in replacement and will provide more amperage.

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