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Old 31-08-2009, 16:51   #1
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Alternator Not Charging Batteries

This weekend I had some trouble with getting my alternator charging the batteries or so it seems. The boat had some questionable wiring practices (running the alternator output line to the same positive lead that powers the starter.) So I simplified and fixed that, but am still having trouble. Here is what I know.
The alternator is a hehr 120 amp externally regulated unit, that I had checked at auto zone and it passed all of the tests, it also happens to have the same style plug as on a 68 camaro. My problem is that I can only measure 11.8 volts coming out the back of the alternator right on the positive screw at idle. Some factors that might be involved are my battery bank for the most part has been staying pretty dead. I don't have power where I am keeping the boat and pretty much constantly drain the batterys by running the lights and an inverter powering a couple fans, its hot in there is an understatement.
The voltage on the batteries before I started the engine was 11.5 so I did see an increase in voltage, but i think it should be much higher. There is a couple of small things I have noticed that while I don't think are the cause may contribute, on my positive lead running out the alternator there is a gooey spot that doesnt feel burned up or broken but the wire just stays gooey odd since it is really far away from any significant source of heat and its surrounded by fiberglass so its not grounding out. Also my belt is on the downhill side of its life but it is still spinning the alternator well and is relatively tight, and isn't making any slipping sounds.
I have tried to trace most of the wires for the regulator as far as I could and drew a picture from memory of everything that I know where goes(See attachments). I just had this alternator rebuilt(ugggh see my post on the key shutting off issue) and before I had it rebuilt the voltmeter on the engine panel would read 14 volts now its not reading anything, probably related to the two cut wires hanging close to the alternator that just run into the wiring harness, that I didn't cut maybe they were just threaded on without connectors? I am really stumped on this and need some major help trouble shooting. Also If anyone has any experience with getting a leaking water pump">raw water pump hose to seal properly I really need to get that leak to stop and am out of simple ideas to fix it.
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Old 31-08-2009, 19:48   #2
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What type of engine do you have?

If you go to any of the on-line manuals, there may be a wiring diagram.

BTW running the alternator output line to the Positive Post on the starter is very common. It eliminates another wire run
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Old 31-08-2009, 21:14   #3
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Are you getting over 13 volts at the positive terminal of the alternator when the engine is revved up a bit?..as measured with the pos end of the multimeter on the pos terminal and the neg on the neg post of the alternator. Start at the source and work your way to the loads.
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Old 31-08-2009, 21:19   #4
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no on the back of the alternator i am only getting 11.8 volts although I did not connect the negative to the grnd on the alternator because of the difficulty of getting to it but im sure the ground i was using was good Also the engine is a westerbeke w27 but the alternator is an aftermarket alternator installed by the previous owner that has a modified bracket and belt to make it fit
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Old 31-08-2009, 21:31   #5
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Your alternator will create voltage whether or not it is connected to a load, if it is working correctly. From what you describe, its not working correctly. Take your alternator into an alternator shop and have them bench test it. They will be able to tell you right away if it working or not and will also be able to tell you what it will cost to have it repaired, the cost of a rebuild or the cost of a new one. I would go the rebuilt route with a warranty....provided of course it failed the bench test. Whatever you do, don't buy a Westerbeke alternator. Its not necessary to waste your money like that for something like an alternator.
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Old 31-08-2009, 21:34   #6
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I suspect the charging problem may be in some way related to the 'not shutting off' problem. Keep in mind, the same ignition switch that would (If is understand the earlier thread) cut off power to the fuel control solenoid.

If the wire that ran to the harness to supply the field voltage is no longer connected your alternator will not charge.

If you turn the ignition on you should be able to read voltage on the field wire on the alternator. If you do not, you might look for a wire running from the ignition switch that is not connected, or may have been overlooked when you hooked the rebuilt alternator back up.

Also, FWIW,

I think the cut wires are a 'red hearing' since the system was charging before, and you know YOU did not cut those wires. They may have been part of the old alternator's regulator... or something else. If they were not cut since the system worked, they are probably not needed.
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Old 31-08-2009, 21:36   #7
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Quote:
Originally Posted by David M View Post
Your alternator will create voltage whether or not it is connected to a load, if it is working correctly. From what you describe, its not working correctly. Take your alternator into an alternator shop and have them bench test it. .....
David,

Maybe you missed this in the OP.

Quote:
.....The alternator is a hehr 120 amp externally regulated unit, that I had checked at auto zone and it passed all of the tests, it also happens to have the same style plug as on a 68 camaro. My problem is that I can only measure 11.8 volts coming out the back of the alternator right on the positive screw at idle.....
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Old 31-08-2009, 21:44   #8
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Ok so next time im at the boat i will trace the wires from the panel into the harness and see where they end up. I recently traveled three hours to the boat only to discover i had forgot my padlock key and had to climb on top of the engine to get in so it is very possible i could have dislodged a wire during this time
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Old 31-08-2009, 21:51   #9
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Originally Posted by pacmaann2 View Post
Ok so next time im at the boat i will trace the wires from the panel into the harness and see where they end up. I recently traveled three hours to the boat only to discover i had forgot my padlock key and had to climb on top of the engine to get in so it is very possible i could have dislodged a wire during this time
Wow, that is lousy. I use a combo lock on the companionway after having to buy bolt cutters.... twice.

I hope that it is something simple, like a wire pulled out of a connector on the ignition switch, or on the wrong terminal on the alternator.

Good luck!
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Old 31-08-2009, 22:16   #10
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Look for the simple things first. (First Lesson taught to me by a Crusty Port Engineer)

Unplugged wire, bad ground.....
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Old 31-08-2009, 23:25   #11
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This weekend I had some trouble with getting my alternator charging the batteries or so it seems. The boat had some questionable wiring practices (running the alternator output line to the same positive lead that powers the starter.) So I simplified and fixed that, but am still having trouble. Here is what I know.
Where did you attach the alternator sense line after you moved it?

The regulator senses system voltage and adjusts output accordingly. If the sense wire is attached close to the alternator it is not sensing system voltage which, due to resistance in connections and old wire could be lower downstream. If the regulator doesn't sense low voltage it won't increase voltage and create a good charge.

Depending on how your system is set up with bus bars etc. I would attach the sense wire either on the primary bus supply or near the batteries (Main switch output side), or back on the starter secondary where it was is usually good as it can sense the voltage from the starter secondary circuit.

If that doesn't help and the wiring is sound, and this is a new problem, I would suspect the external regulator next.
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Old 01-09-2009, 01:27   #12
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Pacmaann,

Before I give you the easiest way of checking this, I must say that you really should rip all out and start over with new wire, cable ties etc. I didn't see many installations that looked worse, the previous owner made a mess of it. A surveyor would cry.

Now for the trick: just remove the field (most cases the smallish blue) wire from the alternator. Get another piece of wire, cut a foot off it and connect the two wires to a simple switch. Put a push-on terminal on the other end of the short piece, check that the switch is off and wrap some electrical tape around the bare contacts. Connect the long wire to +12V anywhere in your system, with the other end reaching the alternator. Pull the field wire from the alternator and connect your home-made "regulator". Start the engine, check the output (should be none) and flip the switch. You should get full output now. Measure voltage from the alternator down to the batteries to check it. If all works, it's the regulator. Measure the voltage at the original (now loose) field wire. It should be 12V. If not, the regulator is broken or has a bad connection somewhere.

The switch can be used for charging when you keep an eye on the voltage and stop charging (flip the switch) when the voltage reaches 14.5V.

ciao!
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Old 01-09-2009, 05:10   #13
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A simple test to see if the alternator field is working is to connect a wire with 12v to the field terminal at the back. This is where an external regulator is connected if you have one. If the front of the alternator becomes magnetized the field is working. I am not sure this works if it internally regulated.

You don't have to run the engine for this test.
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Old 01-09-2009, 08:30   #14
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Thanks for all the suggestions next time I am at the boat I will try some of these field tests
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Old 01-09-2009, 10:18   #15
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All regulators are pretty much wired the same, so print this out and follow the wiring and troubleshooting directions:

http://www.balmar.net/PDF/ars-5instructionsheet.pdf
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