alternator gone bad???

How do you know if the alternator went bad??? When I hooked up my new alternaotr I had a breaker between my new 150Amp alternator and the battery and the breaker tripped...the alternator seems to be charging over 16 volts, which I know is bad, but It could be the guage...and I have been plagued with dead batteries lately, so, who knows???

You may have a short between the pos. and ground.
that would trip the breaker and draw the battery down.

Is the regulator good on the Altenator? The regulator is what reuglates the voltage to 14.4 when the engine is running and turning at different RPM's. In normal electrical systems, when a system rails to it's max voltage, it means there is an open circuit/ it is holding off voltage. I wonder if the battery is shorted causing the breaker to trip and then the 16v into a non load. Anyone know the likelyhood of a battery shorting?

Had a similar problem, but with an older, 50 Amp alternator. The Volt gauge would read around 16 when running, shortly after the breaker would pop. We checked the Bat with boat off and it was fine. Replaced the Alternator, and never looked back. We suspect that the regulator went bad.

As Mike said, check all your connections, 150Amp needs large cables, and check your battery without the engine running. From what I have read, shorts in the system or wire gauges that are too small can cause voltage spikes and breakers to pop. If this is a new HO Alternator, you may have to adjust your wire gauges accordingly.

I am running 4guage from the alternator to the battery...which should be large enough

I have heard people mention the need to change the pulley system when going to larger altenators? Any truth to that?

since the regulator is internal, i don't see why that couldn't have gotten fried.

you can always take your alternator to a shop and have them test it.

Richard:

A breaker in the path between the alternator main output and the battery is BAD NEWS! If that breaker pops then it is almost assured to destroy the alternator.

If you have a circiut breaker in that path then you have to make sure that the breaker be properly sized when you change the alternator. Since the breaker's primary responsibility is to protect the wiring, changing the circuit breaker size will dictate that you install larger wires to everything that the circuit breaker fed. (which is usually the main wiring harness up to the dash).

To get an idea of what your alternator is doing get a multi-meter and measure the voltage at the battery. If the battery is fully charged you should have 12.5 to 12.7 volts at the battery. With the engine running, even at idle, the voltage should come up to 13.0 volts. If the battery was really discharged, reading 12.0 or less before you started, then the voltage might not rise that high until the engine RPMs come up above 2000 RPM.

Raise the engine RPMs to 2000 RPM. The battery voltage should be at least 13.2 volts, and not exceed 14.2 volts. If you have a 150 amp alternator then I would expect 14.2 volts at any engine speed above idle unless the battery was really dead.

and if it is charging above 14.2 volst then the regulator (self regulated) is shot???

Hey Rod: You keep posting about these Marine alternators that should be pushing 14.2 volts when the batterys are dead. Where can I get one of these alternators because I never see or have heard of sutch High voltage. I have asked you about these high volatge #'s in the past and your answer is un-clear. Either I have somthing hooked up wrong or my alternator belt is slipping ormy alternator is no good. Or your crazy. I have asked all my friends with HO alternators what there voltage is after playing for some time and we are all in the same voltage, Ill explaine
The only time I see high voltage #'s is when my 5 Blue top batterys are fully charged. Ill see like 13.5 volts at Idle. Then after a day of pounding my stereo Ill fire it up and my batterys will be real low and I see like 12.1 or 12.3 volts thats above Idle. Ill have to have everything off and be over 2000 RPM's and the voltage will slowly start to raise. I have a Dakota digital voltmeter and I have checked it against a FLUKE multi meter for the back of the alternator and they are very close in there #'s so I know the gauge is correct