Alternator fluctuating voltage solved??????

[Bruce Sevier]

Our 1999 Beaver Marquis has had a problem with the voltmeter on the dash and the Silver Leaf system showing voltages from 13.2 to 15.2 volts, the gauge on the instrument panel constantly moving, headlights & instrument lights going bright to dim in a pulsing rhythm, warning light on the inverter control panel flashing on and sounding a alarm, and something else I probably missed.  I read most of the posts about this issue, and had the alternator rebuilt (new brushes and regulator), but still had the problem.  One or two mechanics and some of you in your posts suggested this could be caused by a bad ground.  I cleaned all battery terminals and cable ends, but the problem persisted.
The house batteries have a red and black wire (probably 10 or 12 gauge) with ring terminals attached to the main 12v pos and neg terminals.  I have no idea what they are attached to in the coach, but after close inspection I found corrosion in the wire near the terminal.  I cut the wire back to clean wire and added new ring terminals.  This fix seems to have solved the fluctuating voltage problem and now I have 13.8 to 14.2 fairly constant voltage and no alarm from the inverter control panel.
Does anyone know where these red and black wires go?  I suspect the inverter or the instrument panel, but am not sure.  The alternator is a Leese Neville model BLHA2070VE, with external regulator, and external ground.  Is this what was referred to as a Bird system I read in a previous post?
Any comments, suggestions or possible answers would be greatly appreciated.
Thanks
Bruce Sevier

[Mike Groves]

Given that I saw this problem in my coach 3 years ago and having had the alternator rebuilt twice since then and that my coach is a 1999 I am very interested in finding these two wires.  But did you mean "house batteries" or "chassis batteries"?

Happy New Year to all of you,
Mike

[Gerald Farris]

Bruce,
Your coach uses a battery isolator and Duvac alternator, therefore it does not have a "Bird" system.

There are 4 wires to your alternator. The 2 large wires are for output and ground. One of the small wires is ignition feed so that the alternator has a current source to magnetize the rotor to produce electricity. It runs from the ignition circuit in the LF electrical bay. The other small wire is the sense wire that tells the alternator voltage regulator what the current is at the chassis batteries. It runs to the chassis batteries. There are a few coaches where the sense wire was ran to the house batteries, but it does not matter because both battery banks are receiving the same charging current from the battery isolator. 

Gerald

[Dan Stussi]

I had the same issue on our '98 Monterey when we bought it. I found the sense wire at the alternator had been broken, and a feeble repair had been made. Fortunately there was excess wire so I was able to put a need end on it, and just like magic all was good.

Happy New Year,

Dan

[Bruce Sevier]

Thanks for the replies, greatly appreciated.
Mike:
To clarify from my post, the red and black wires are attached to the house (6 6v) batteries.  These wires go towards the front of the coach on the frame, but do not know what they connect to.
Gerald and Dave:
The white wire on the back of the alternator is attached to the voltage regulator, this has 12v all the time.  The black wire is attached to the large output wire, and goes to a fuse and on into the wire loom.  Is this the sense wire?  Since it is attached to the large output wire on the back of the alternator which I assume makes a connection at one of the terminal studs mounted on a flat piece of steel near the batteries.  I did replace the ring terminal on this black wire, which I assume is the sense wire you have described so possibly this is actually was the fix to correct the fluctuating voltage.
Thanks again, Happy New Year
Bruce

[Bruce Sevier]

Oops
I meant Dan, not Dave, sorry

[Gerald Farris]

Bruce,
It sounds like your coach has had a conventional truck alternator installed in place of the Duvac alternator that it originally came with. The difference is that a conventional alternator is designed for a system without a battery isolator, therefore the output terminal on the alternator always has battery voltage. A Duvac alternator is designed for use with a battery isolator, so there is no battery voltage at the output terminal, therefore it has two small wires at the voltage regulator, an ignition wire and a sense wire.

It sounds like your alternator had the ignition wire ran to the output terminal in an effort to get around the absence of battery voltage at the output terminal. This arrangement should work, but the ignition wire will be receiving about 1/2 a volt higher than it should unless it has a diode installed (which it may have) because the alternator has to produce the higher voltage to overcome the resistance in the battery isolator to get the voltage at the desired point on the sense wire.

Gerald