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Old 05-03-2015, 09:54 PM   #1
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Diode Isolator/ Solve This Please

Hey Guys,
I found this post from 2013 1984 Vogue II - Can you identify what is in the picture? I need help. I have an alternator that's not putting out power. Unable to find anyone to bench test so I bought a new one. Old one, 2600jb, had 4 posts with wires connected. New one, wilson 90-04-7039, has 2 posts + ground. Leftover wires are yellow, small gauge, previously attached to a thin long post above (+) and a green small gauge previously attached to a thin short post right of the ground wire coming out of alternator. I wrapped these wires in electrical tape and did not hook them to a random post in fear of frying the $300 alternator. The battery is still dropping volts when running after installing new alternator rather than putting out 13.5+. Also back of alternator posts are reading .14 and .28 at idle and on throttle. Battery Volts drop from 12.55 to 12.28 when running. I'm wondering if the problem was not the alternator to begin with. Also wondering how to properly place the two leftover wires. Suspecting a diode isolator issue as in previous post. Mainly concerned with using my RV instead of bathing in pumice. Would love some help.
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Old 05-03-2015, 10:12 PM   #2
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Google 4 wire alternator.

I think you two extra wires are charge lite and ignition.

You may need to jumper a connection

Dan
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Old 05-04-2015, 08:36 AM   #3
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Thanks Dan, when googling 4 wire alternator I haven't been able to find anything that looks like mine. One of the mystery wires (yellow) attaches to the L post of the diode isolator. The wire originates at the alternator but the wire's end lug is too small to fit over the (+) or (-) post of the alternator. The green wire could potentially be an ignition wire. I believe it travels to the rear start panel in the engine compartment.
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Old 05-04-2015, 09:39 AM   #4
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Old wires may be ignition to control field when engine is running and other likely is for dash light.

Your new one may be fully self contained but that is only a guess.

You should work with the supplier of the new alternator as they should be able to tell you what you had and how the new one works.

New one may need to see voltage on the connections and if your mh has a diode type isolator then thst will not happen.

Old one may have used one of the smaller wires to supply field power thus allowing it to work.

Do not guess!

You are doing right so far but go back to dealer and get good information.

Post what you have so others may help with specific to your coach data.
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Old 05-04-2015, 11:00 AM   #5
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If you have a diode isolator, there will be no feedback to the alternator regulator. To counter that, they run a wire from one of the battery terminals, on the isolator, back to the regulator voltage sense terminal, on the alternator.

The other wire may be key switch power, to turn on the regulator.

Before you go any further, test your isolator. Use the diode check mode on your ohm meter.

You should hear the tone, with red lead to center tap and black to both sides, but no tone with red lead, from either side to center tap.

If you get no tone, jump the center tap to the tap that has the yellow wire. If it charges, the Isolator is bad.

I hope this helps, Good luck
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Old 05-04-2015, 01:18 PM   #6
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Thank you for the replies. Just got back from an alternator/starter man who looked at my old alternator. He said the two additional posts were add-ons and couldn't extrapolate where they might have gone. Either way it was bad. I am thinking my problem is in the isolator to alternator regulator connection. I'll use the Ohm meter test to check tonight. It sounds like the regulator voltage sense terminal is what was added to the old alternator and not present on my new one. With engine running at idle posts on alternator test: 0.14 and 0.28 at 1500 RPMs. Not 14, 0.14. I believe there is no call to produce power. The yellow wire comes off the engine battery side of the diode isolator and was connected to a post added to the old alternator. New alternator does not have this post only has (+), (-), (ground). Can that wire be piggybacked on any other posts on the alternator?
1984 Vogue II
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Old 05-04-2015, 01:33 PM   #7
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I too believe that the other unaccounted for wire is the key switch wire. The engine starts reliably from the rear engine compartment panel but only occasionally from the front drivers seat. Assuming these are the two wires, 1) supply wire to regulator voltage sense terminal 2)key switch wire. Anyone certain where to post those on this model alternator Leece Neville 90-04-7039? I'll try to take some pics and upload tonight.
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Old 05-04-2015, 02:02 PM   #8
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With no sense wire, the alt will go to max output and can blow, diode type isolators. ( seen it )

Move 1 wire from isolator " battery " terminal, to the isolator " alternator " terminal.

If the alt works, you need to use a BIRD in place of the isolator.

Single wire alternators, internally check battery voltage, to regulate output. The diode isolator blocks that from happening.
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Old 05-04-2015, 08:33 PM   #9
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My cheap digital multi-meter does not have a tone but does show resistance or lack there of in ohm readout for diode testing. Red on center = measurable resistance (L post:500's and R post: 600's) Black on center = 1. I think I need a BIRD from putting together the pieces.
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Old 05-04-2015, 08:36 PM   #10
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Hey Twinboat, to test the alternator you are saying I should move the engine battery wire off of the L terminal on the isolator and to the center terminal, piggybacked with the alternator wire? Then start the engine and see if it puts out volts on the posts?
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Old 05-05-2015, 04:26 AM   #11
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Yes, the alt will see power and be able to regulate it. If it works you could leave it that way. It will charge both batteries and isolate the one still connected to the other post.

Good luck
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Old 05-05-2015, 05:29 PM   #12
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So I piggybacked the alt and engine battery on the isolator and still only getting 0.14 out of the alternator. The search goes on.
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Old 05-05-2015, 06:20 PM   #13
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Do you have 12 volts on the alternator wire? There needs to be.

Put a jumper cable on the alt wire to the positive terminal of a battery

If that don't work, use a jumper to ground the alt negative terminal to battery negative.

All you need to make juice, is
a battery and a spinning alternator, if its a 1 wire alternator.
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Old 05-05-2015, 06:23 PM   #14
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It is a 2 wire alternator, plus the built in stator trio wire.
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