An alternator quickie...

[SVPrairieRose]

Hey guys, looking for some quick advice here. I am almost half way to mexico and I am stuck in San Fran with a compounding list of issues, one of which is about to fly home if her boat isn't fixed soon!

The alternator is where I need a bit of help. It no longer puts out any charge at a low idle -600rpm, and puts out a very varied charge (60-90amps) at operating rpms.

it is an externally regulated 140amp alternator with a xantrex regulator.

Any advice would be appreciated, thanks guys.

Rob.

[dkenny]

you might have lost a diode. or a brush might be sticking(not making full contact)
what's the output voltage?

-dkenny

[NICHOLSON58]

I found our alternator not putting out. 14 of 16 diodes were fried as was the regulator. I had the alt rebuilt at a truck alternator and starter repair shop for 68 bucks. We replaced the regulator with Balmar. Problems gone. I assume lighting strike. Lots of other electronics were dodgy too. Presented an opportunity to upgrade a lot of toys.

[TQA]

Any decent alternator repair shop can test run the alternator on a rig and see if under full field current conditions it is giving it's rated output and if it is steady.

If it is then your belt [s] might be slipping.

Last port of call would be the regulator they usually work or fail completely.

Why not get a basic auto alternator with internal regulator as a back up and GO!

[ebs001]

First thing to do is to check your fan belt. If it's glossy that is probably your problem. Check the tighness too. After that if you have a Balmar call their service department. They will walk you through some test that you can do with the alternator still attached to the engine and test the regulator. If that yields nothing then a repair shop is your next step. A basic auto alternator is a good back-up as suggested above.

[LakeSuperiorGeezer]

The fact that amps varies may not be a problem. Put a digital volt meter on it and see if the voltage is constant. However, no amps at idle points to a diode problem as would low voltage.

[Capt Len]

It takes about half an hour to switch them so put on the spares and take the suspects to a shop for any necessary work But check the belts or replace from stores before going to this effort or to sea .