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Old 14-08-2015, 15:41   #1
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Alternator Problem Yanmar 6LP

I have a single Yanmr 6LP, 2004.

My alternator was only putting out just over 13v with the engine running, so i assumed it was weak. I purchased a new alternator 80amp, direct replacement.
I installed it, and wired it as previous alternator.

the new alternator got very HOT quickly and slight smoke before i shut it down. it was putting out only 13.2 volts.
i plugged the wires on the plug on the backside and started again, this time no Voltage from alternator or smoke.

I have stopped trying things as i dont want to blow the new alternator, nut have no idea why its doing this? is there something else on a yanmar engine wireing loop that could have failed causing this problem?

many thanks
Hamish
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Old 15-08-2015, 06:37   #2
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Re: Alternator Problem Yanmar 6LP

Greetings and welcome aboard the CF, Hamish.
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Old 15-08-2015, 18:38   #3
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Re: Alternator Problem Yanmar 6LP

Quote:
Originally Posted by family cup View Post
I have a single Yanmr 6LP, 2004.

My alternator was only putting out just over 13v with the engine running, so i assumed it was weak. I purchased a new alternator 80amp, direct replacement.
I installed it, and wired it as previous alternator.

the new alternator got very HOT quickly and slight smoke before i shut it down. it was putting out only 13.2 volts.
i plugged the wires on the plug on the backside and started again, this time no Voltage from alternator or smoke.

I have stopped trying things as i dont want to blow the new alternator, nut have no idea why its doing this? is there something else on a yanmar engine wireing loop that could have failed causing this problem?

many thanks
Hamish
I think you have already fried the new alternator.

There could be a shipload of things wrong that might be killing your alternator but you have done the right thing in ceasing this replacement method of troubleshooting.

Unless you are fairly electrically literate, troubleshooting by the internet may not be your best approach IMO; might be time to call your local marine sparky if you are in a location that is well serviced by marine trades.

Welcome aboard and sorry that your first post is one about possibly an expensive problem.
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Old 16-08-2015, 11:18   #4
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Re: Alternator Problem Yanmar 6LP

Hamish, welcome. In order for us to help you, we need some more info. Please confirm that it was a direct Hitachi replacement alternator? [I know you did say it was a direct replacement] External or internal regulator? If external, what settings?

You may be unaware of the Hitachi alternator issues:

Hitachi/Yanmar Alternators: (by Maine Sail)

Some alternators though, such as those made by Hitachi and found on Yanmar diesels, are dumber than a pound of beetle poop. Actually, to the alternator, they are pretty smart but to your batteries and the speed of charging they are flat out stupid. Why?

Hitachi alts with dumb regulators, and some others, limit voltage but also reduce voltage based on alternator temperature. This is a self protective feature installed in the internal dumb regulator to prevent the alternator from cooking itself. Remember voltage is the pressure that allows more current to flow. So, if we reduce the absorption voltage, then we also reduce the current the alternator is supplying.. The battery simply will not accept the same current at 13.4V that it did at 14.4V and as a result the alternator will run cooler. What do you suppose this does to your batteries over time.......?

The problem is that when cold you will get 14.3V to 14.4V out of the Hitachi but as the alternator heats up the dumb regulator begins to reduce the CV/voltage limit based on the alternators internal temperature. It is not uncommon to find a Hitachi alternator at 13.4V when hot. This is REALLY, REALLY DUMB....

If you have a dumb regulator, and notice the voltage dropping, it is likely a temp compensated dumb regulator. Get rid of it or plan to buy new batteries more often.

If you have a temp compensated alternator or a Hitachi alternator on a Yanmar you really are in dire need of external regulation if deep cycling a larger battery bank.

This is from:

Musings Regarding External Regulation - SailboatOwners.com

and these, too:

Hitachi Alternator and Smart Regulator Instal Question


Most practical way to upgrade Yanmar alternator?
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