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WonderG

Alternator Voltages, Connections, and Charging

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WonderG

Please help me straighten out a alternator charging problem. I can't get the 14+ volts while the engine is running. I've tried several things, but I am at a loss to get it right.

I have a 2001 Wakesetter VLX and a two battery setup with the Perko switch.

I used a battery charger to get a full charge and these voltages that I read.

At the alternator, across the POS and NEG terminals = 14.38V, across the NEG to EXC terminals = 13.55V. At the battery I am reading 13.99V.

The orange wire is attached to the POS terminal, this is the charging wire, correct?

Is the NEG grounded to the engine block?

What is the EXC terminal? Is that feed back to the alternator? What voltage should I have there? Where does the the other end of the wire attach?

Why can I not get 14.7V? Any ideas?

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nuttyskier2002

Please help me straighten out a alternator charging problem. I can't get the 14+ volts while the engine is running. I've tried several things, but I am at a loss to get it right.

I have a 2001 Wakesetter VLX and a two battery setup with the Perko switch.

I used a battery charger to get a full charge and these voltages that I read.

At the alternator, across the POS and NEG terminals = 14.38V, across the NEG to EXC terminals = 13.55V. At the battery I am reading 13.99V.

The orange wire is attached to the POS terminal, this is the charging wire, correct?

Is the NEG grounded to the engine block?

What is the EXC terminal? Is that feed back to the alternator? What voltage should I have there? Where does the the other end of the wire attach?

Why can I not get 14.7V? Any ideas?

Where are you getting 14.7 volts from? 13.99 to the battery is fine. That falls between 13.8 and 14.2 which is right where you want to be. To answer the question about the exiter, on many applications that wire goes to the batt side of the solenoid starter. It serves 2 purposes. 1st it provides the initial current to get the alternator to charge before it starts developing its own voltage. 2nd after the alternator starts to charge it (the exciter wire) provides a feedback of what the voltage is at a given point.

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WonderG

Thanks for the reply and the description of the exciter connection. I had no idea of where that was connected. I get the 14.7V from the read out on a couple of other Malibus and a little research on the web.

The problem is when the alternator is put under load,(to power the amplifier and such)the voltage falls way off. I start getting closer to 12.5V. Please keep in mind the voltage was with a fully charged battery and no load. Is this normal or should the alternator adjust to keep pace with the demand? Even with low volume and low demand it doesn't seem to do the job of keeping the battery charged. I've always put a battery charger on after long days to compensate.

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Bawshogg

You may have either to much amperage load total, which the alternator cannot keep up, or there could also be an issue with the regulator on the alternator. I don't know what size alternator you have, nor the demands you have running on your electrical system. Have you already replaced the alternator? Just know that the regulators function is to provide the correct voltage for the a given load, if your loads are exceeding what your alternator an handle, your battery voltage is gonna drop.

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Pistol Pete

The stock alternator output on that boat is only 70 amps. That's not much if your driving a large stereo.

Also remember, you're only gonna get 70 amps out of the alternator if there is a large demand on the charging system and if the motor is running at greater than about 2K rpm.

You might need a larger output alternator upgrade, capacitors, or on board charger.

How big is your stereo? What components?

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WonderG

I have two amps and I understand the alternator not being able to keep up when the amps are really working. We took the boat out today and I even watched the volatage drop when we ran the engine up to 3500 rpm and better. No radio even on. How do I test the alternator without taking it off?. I've taken it to the auto parts store, but they couldn't do it.

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WonderG

I've been doing some research for a higer output alternator, if I can't get mine right. What alternator would replace a Leece Neville 8MR2084k?

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Pistol Pete

You can test the output of the alt. at the batt. with the motor running with a clamp style amp probe and multi meter.

Got any mechanic friends with that sort of thing?

Most guys take their stock alt. off and send to an electrical place to have it re-wound. It has to remain marine rated. I think you can get about 100 amps out of a re-wound alt. with a smaller pulley.

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WonderG

I am getting a new alternator today. Any adivce? Any do's or don'ts? Any lessons learned that should be shared? I'd appreciate the help.

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