Alternator problems?

[maelduin]

After turning the battery switch off while running I have taken some readings with a multimeter and hoping someone may narrow down what might be happening and whether it might be a diy project, as if I need another. After disconnecting the alternator had a diode test of about 870, nothing when reversed. DC current when running is 14.75 and AC jumping around but over 2. As you can tell I need help. I sure would appreciate any thoughts. Thanks.

[model 10]

Not all systems do that but yours does, to bad. So pull the alternator off, open it up and change the diode assembly, piece of cake, minding the brushes of course.. You should add the little gadget that keeps that from happening.

[maelduin]

Thanks Guy! By the way, what do you call that little gadget?

[Blue Stocking]

Originally Posted by maelduin

Thanks Guy! By the way, what do you call that little gadget?

ZapStop.

[tkeithlu]

It's called a transient spike protector. Balmar makes one.

[Stu Jackson]

Originally Posted by tkeithlu

It's called a transient spike protector. Balmar makes one.

Correct, that's the real name for the zapstop.

But you don't need a zap stop if you wire your alternator output to the house bank, and just use the switch as a USE switch, not a charging determinator switch.

Been beaten to death on this and every other electrical boating forum known to man.

Like this:

Basic Battery Wiring Diagrams This is a very good basic primer for boat system wiring: Basic Battery Wiring Diagrams

This is another very good basic primer for boat system wiring: The 1-2-B Switch by Maine Sail (brings together a lot of what this subject is all about)
1/BOTH/2/OFF Switches Thoughts & Musings | SailboatOwners.com Forums

The Short Version of the 1-2-B Switch Stuff: Electrical Systems 101 This is a link to the Electrical Systems 101 Topic, reply #2

What are ACRs, Combiners & Echo Chargers? (by Maine Sail)
Battery Switch Question ? | SailboatOwners.com Forums

[tkeithlu]

Wow! That's wonderful. I had not really thought about it, but that's the way my main alternator is wired - directly to the monster positive bus to the house batteries. There is a switch in that line, but I have not turned it off since the boat was launched. The battery selector switch is just what you say- a use switch, not a charging path switch. Thanks.