Intermittent Charging from Mando 55A Alternator

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Jun 9, 2013
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Trying to troubleshoot an intermittent charging condition from my Mando Alternator. I read several threads and as a result, decided to examine the wires. I noted the following. Where the wires go through the grommet and into the back cover, the wires are corroded frayed and the exterior coating is missing. Description of the intermittent charging: Boat is equipped with only a volt meter. After start, the usual brief period of charging does not occur. After repeated starts, the voltage drops down to 10 or so and still no charging. Other times while cruising to a new fishing spot, I will notice full charging about 14 vdc. Placing a load on the system, (horn, lights), does not result in charging

1st question: If I remove the alternator and then the cover, would I be able to make an effective repair in that area?

It is possible that the wires, although in poor shape, might not be the problem. I have seen repair kits on the internet.

2nd question: Does anyone have a good number for the proper kit to install? The kits seen have bearings, brushes and regulator.

The label on the alternator is damaged. The only numbers I can read are AR 150.

3rd question: Is this a complete number, if not can anyone fill in the missing parts? :)

I installed two batteries in the boat and a A, B, Both switch. It all seems to work very well.

4th question: Is there any caution or info I might need to know about such a setup.
 

Fishermark

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Oct 19, 2003
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Re: Intermittent Charging from Mando 55A Alternator

I would suggest either taking it to a local alternator shop if you have one - they can rebuild it. Or buy a new one. I'm sure you can find a kit... but you can find a new one for not much more than you can buy a kit. Here's one for only $69. (I would be worried that it has more amps - it will only put out what you need. If it isn't the right one you can look around on the site. I have ordered from them before with good results.

You will also need to fix the wiring regardless of whether the alternator is bad or not.
 
Joined
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Re: Intermittent Charging from Mando 55A Alternator

Alternator-1.jpgAlternator-6.jpg
Here's one for only $69.

You will also need to fix the wiring regardless of whether the alternator is bad or not.

That's not a bad price. Including shipping to my door, it would Be $95.00. I know you could not see the wires, but they are bad only at the grommet going into the alternator. If I replaced the alternator, they would be cut off anyway.

When looking at the wires, I have 4, the large orange one, a black, a Purple and a Red. The one pictured in the site has only a nut for the Orange wire, and a red and a black.
The picture of the DB alternator shows a place for the large orange on the outside of case. I do not see a spot for the Ground wire.

Question: Do the two wires going into that plug in the DB picture equal the Red and Purple that I have?
 
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Fishermark

Vice Admiral
Joined
Oct 19, 2003
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5,617
Re: Intermittent Charging from Mando 55A Alternator

Your picture is almost too small to see. It appears from the manual, that your red wire is the "sensing" wire - it should always read 12v.

Your purple wire should be the "excitation" wire - only have 12v when the switch is turned on.

As you mention - the orange is the main output lug on the alt - the ground is simply grounded to the case. You can kinda see it in the pic below.

Here's a close up of the back of the alt I posted above:

wolthuis.aspx
 
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Joined
Jun 9, 2013
Messages
20
Re: Intermittent Charging from Mando 55A Alternator

Thanks for the info. I did find the repair kit for the Mando. The wires that are frayed and corroded are the wires that go into the regulator. I removed the regulator and the wires are potted into the regulator assembly and would be extremely difficult to repair. It does look like the wires are the only issue. They are either not making connection or are shorting each other, or the regulator could be faulty.
The new regulator comes with the wires ready to install.
Mando Marine Alternator Repair Kit | eBay
it's a not much less then the new alternator, but the E-Bay store is right here in Michigan and the parts should be easy enough to install. I don't mind doing the work.
 
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