Alternator question

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Alternator question

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Alternator question

Postby Grasshopper » May 11th, 2017, 5:08 am

Guys,

My truck only seems to put out 25V at the alternator which seems a little low to me; I would have expected 26-27 volts at least, and the volt meter on the dash reads in the yellow section instead of green. What is typical voltage output for an M151A2, and are there any servicable complonents in them? I have had success with other ex-military alternators by way of cleaning the ametaures and brushes, and I suspect this Alternator may not be in the first flush of youth.

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Re: Alternator question

Postby kmam » May 11th, 2017, 6:55 am

There is an excellent document on adjusting the alternator. It is bed time here but if you have not located a copy by tomorrow afternoon our time I will dig it up and get it to you.

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Re: Alternator question

Postby Horst » May 11th, 2017, 2:37 pm

for sure too low. It should be around 28V or at that little indent in the green arc. You can try to adjust it, remove that little cap where the connections are and below you will find an adjustment screw. I have a little doubt however that is it simply out of adjustment and it might need more work to it.
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Re: Alternator question

Postby kmam » May 11th, 2017, 3:55 pm

The document you want is "Charging System Troubleshooting - The Easy Way", DA Pamphlet 750-33 dated December 1976. It is an excellent document that will guide you through the steps necessary to get everything back to spec.

If you can't find a copy pm me.

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Re: Alternator question

Postby svramselaar » May 12th, 2017, 1:38 am

hi

before adjusting
battery`s must be full
use a good digital voltage meter
take the Allen plug out next to the little wiring box
to adjust use a small Philips screwdriver
let the mutt run no lights or els on
voltage can be set til MAX 28.8 it depends witch type of battery`s
normal is 27.5 - 28 volts

george
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Re: Alternator question

Postby Grasshopper » May 12th, 2017, 4:06 am

Thank you for the tips and advice gentlemen, I now have a copy of the document. I did learn how to rebuild and set up alternators as part of my apprenticeship as a bus/truck mechanic, but not really touched one for years as the common thing to do nowadays is just to change them out (plus the fact I've been working on the railways for about 14 years now so the stuff we have is much, much bigger!).

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Re: Alternator question

Postby Grasshopper » June 14th, 2017, 4:23 am

Just an update - initial findings from following the DA Pamphlet 750-33 suggested that the alternator regulator was U/S. I looked for the adjustment screw, but couldn't initially find it as the alternator is in a pretty poor external state. I did find what I believed to be the remnants of the plug, got brave and drilled through it (in situe) and found the adjuster screw. I adjusted it and now charging at 28V. :) I think some previous person had shorted the plug to the battery cable, which resulted in the plug disintegrating flush with the alternator casing (which is why I couldn't initially find it). I did remove as much swarf as I could with a magnetised screwdriver, and will plug the hole with silicone after my next run out and a re-check of the charging voltage.

Thanks for the help,

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Re: Alternator question

Postby Fil Bonica » June 14th, 2017, 10:57 am

Kind of scary drilling out plug.
Hopefully you were successfull in getting out the filings.
You could pull off the end cap and clean out the regulator.


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Re: Alternator question

Postby Grasshopper » September 6th, 2018, 2:27 am

Just an update on this - while I usually get 27-8V, on occasion the dash gauge sometimes just sits on the edge of the yellow and kicks out 25V. I quick touch (no adjusting) of the adjuster pot returns the reading to 27-28V so I think the pot is either dirty or on the way out. Question is the pot mounted on the regulator and if so, is my A2 likely to have a 60A alternator? I can get regulators easily from the European dealers, I just need to identify which one I require.
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Re: Alternator question

Postby Fil Bonica » September 6th, 2018, 9:07 am

Brand of alternator ?
Model number?

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Re: Alternator question

Postby acudanut » September 10th, 2018, 4:25 pm

Are you sure it is Alternator and not a Generator ? Never heard of a alternator in a M151.
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Re: Alternator question

Postby kmam » September 10th, 2018, 5:09 pm

25 Amp - Generator
60 Amp - Alternator
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Re: Alternator question

Postby Fil Bonica » September 10th, 2018, 5:38 pm

There is no reason that a 151 cannot be retrofitted with an alternator.


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Re: Alternator question

Postby rickf » September 10th, 2018, 6:25 pm

That should say no reason a straight or A1 cannot be retrofitted since the A2's all came with the 60 amp alternator.
1964 M151A1
1984 M1008
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04/1952 M100
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Re: Alternator question

Postby Fil Bonica » September 10th, 2018, 8:18 pm

Ah yes,
A grammar lesson!

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