agood1
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With dead batteries?
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Alternator Crashed
- Thread starter 3rdmdqm
- Start date
There is dead, and then there is dead. If your batteries were totally dead, putting out less than what was necessary to start up the field, your alternator will put out zip... nada...and they will stay dead. If, on the other hand, they were too dead to start the truck, they may still be alive enough to run the alternator. It takes several hundred amps to crank the truck, but only a couple of amps to run the field.
Remember, you jumped the truck. The alternator started building with the power from the batteries you used for the jump, and then continued charging your deadish batteries after the jump battery was removed.
-Chuck
agood1
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There is no alternator made that will charge "stone dead" batteries. Not sure what your point is here?
Somemedic
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opcorn
agood1
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Because you stated that your alternator(s) started charging immediately when you start your engine, but you stated earlier that it would take current from the batteries to start the field. So my question was, if you had dead batteries how would you get current to your exciter to start the field? Assuming that none of these alternators are one wire connection.
And I have to assume in your example that if I pull started my truck with dead batteries, and did not jump it...then I would have needed to put current to the field to get the alternator charging again. Right?
That is correct, but one wire alternator, or external regulator is not an issue. No battery, no field current, no output from the alternator.
-Chuck
agood1
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Good, Thanks for the replies.
agood1
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Exactly my point.
Gamagoat1
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It seems an overlooked item concerning these alternators is the fact that they have a brush.
I've had two fail because the brush had either worn down too short to reach the com. or had gummed up and did not contact the com.
Check out TM 9-2920-225-34, both found here on SS
I've had two fail because the brush had either worn down too short to reach the com. or had gummed up and did not contact the com.
Check out TM 9-2920-225-34, both found here on SS
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Brushes usually last around 80 or 90,000 miles, and then they are too worn out to make reliable contact. I am starting to get quite a collection of car and truck alternators around here whose only problem is worn out brushes. Since we don't really know how many miles we have on our deuces, it is a good idea to check the brushes first when you are getting strange behavior from your alternator.
-Chuck
Gamagoat1
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It's surprising how many people don't realize that there are brushes (1) in these alternators
3rdmdqm
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Where would one get replacement brushes for these if that is the cause? I purchased a new alt from avengeusa, but I'm going to take the old one apart and dabble with it to see if I can repair it and use as a spare.
Gamagoat1
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Probably any generator/starter rebuild shop would be the first guess.
I use paint thinner to get all the grease off the brush. It doesn't have to soak just wipe it off clean. A Q-tip with some thinner will clean out the brush holder. Try not to get thinner on the commutator or windings. The main thing is to make certain that the brush moves freely and that it makes good electrical contact with the commutator at all times.
I use paint thinner to get all the grease off the brush. It doesn't have to soak just wipe it off clean. A Q-tip with some thinner will clean out the brush holder. Try not to get thinner on the commutator or windings. The main thing is to make certain that the brush moves freely and that it makes good electrical contact with the commutator at all times.
There shouldn't be any need to clean them. They generally keep themselves clean throughout their life time. They are made of graphite, which is slippery stuff. The only issue is if they get loaded with mud and gunk for some unusual reason (swimming). Then they can be washed down with just about any gentle solvent... Naptha, lighter fluid, CRC electrical cleaner...even water if you dry them out.
If you find yourself removing the brush, only to put it back it, be certain that it is put back in the same orientation as it was in before you removed it.
NAPA is a good source for brushes, but I don't have any part numbers. If you can figure out what the 12V equivalent alternator is, its brushes should be the same. If you bring the old brushes in, the NAPA counter guy should be able to find a new match.
Remember, there are TWO brushes.
-Chuck
Gamagoat1
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Check out TM 9-2920-225-34 and TM 9-2920-225-34P, Both available on SS for download. Gives all you'd ever want to know.
The brushes do get greasy if the seal on the rear bearing has failed. The carbon will absorb oil.............
The brushes do get greasy if the seal on the rear bearing has failed. The carbon will absorb oil.............
If the seal on your sealed rear bearing has failed, and you are getting enough oil to wet the brushes, you are going to need a new rear bearing, so your brushes aren't a major part of your worries.
-Chuck