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Thread: M1009 Gen 1 issues- im confused

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    4 Star General davidkroberts's Avatar
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    Default M1009 Gen 1 issues- im confused

    Hi crew,ive got a strange problem with a M1009 picked up. When i got it the #2 altenator's two wire plug was melted at the alternator and the wires were not connected. The alternator also was smoking whenever current was put to the truck running or not. The Gen1 light lights up when the key is turned on and stays on when its running.

    I replaced the #2 generator and fixed the plug and am not having any issues with it anymore i think.

    Gen1 wasnt engaging and had no power going to the 2 wire plug. I fixed it by wiring it directly to the firewall plug block where the wiring diagram says it goes.

    Before i found the wire not being hot I had replaced the Gen1 altenator. i ran a jumper wire from the Gen 1 alt hot post to the plug which was probaly pretty dumb looking back on it. Once i figured out that the altenator wasnt the problem i replaced the old alt and tested t with thejumper wire. The battery gauge never read in the green but just barely. Later duringthe test (still on the jumper wire) the Gen1 light came back on. Bu it worked for a half hour before coming back on and stopping charging.

    Did I burn out the alt with my jumper wire stunt (likely)? Is something else going on. I am going to get another alt tomorrow without my stupid stunt with a jumper wire.

    I am not very good with electrical stuff and could use some help.
    Dave in Tenn

    19?? M818 tractor
    1985 Bombardier Iltis
    196? M35A2w/hardtop
    196? M35A2 W/softop
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    1966 M101 3/4 ton trailer

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    General 1stSarge's Avatar
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    Dave - Jumping the hot lead to the #2 position on the plug should not have done any harm, jumping it to the #1 position might have.

    Iím not real clear on what exactly you did, you say you replaced the #1 alt, then tested the circuit, and found the feed not connected, then put you old alt back in and this is the one that failed after a half hour? So then it sounds like you still have a new one laying around to swap out, why are you going to get another one?

    Sorry for being thick headed, just trying to get a grasp.

    The Alt1 #1 plug feed comes directly from the Gen 1 light with only the bulkhead connector in the circuit. The # 2 feed comes from the hot side of the 12V for the truck. Make sense?

    To further my EWAG, if you did hurt the alt, it would probably be the voltage regulator that took the brunt of the damage, testing and replacing the components in the alt is WAY cheaper than replacing the alt.

    Very low batteries will sometimes make the gauge read in the yellow, as well as poor/dirty/loose connections anywhere in the circuit.

    Hope any of this helps.

    Post back when you get back to it.


    ---John

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    The volunteer Fire Dept. that i am on has a 1985 m1009 and the gen2 light comes on when you turn the swith on but not the gen1. Once you start the truck the gen2 light cuts off but the batteries are still not charging. Is the Gen1 light supposed to come on when you first cut on the switch and could this be the charging problem? Any suggestions will be greatly appreciated.

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    4 Star General cpf240's Avatar
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    Both GEN lights should come on when you have "key on, engine off" and go out once the engine is running and the alts have reached the proper rpm to start charging, sometimes requiring a blip on the throttle. If the GEN bulbs are bad, the associated alt will not charge. Remember that the bulbs are different, as the GEN 2 bulb is 24v while GEN 1 is 12v.

    Read the alt troubleshooting section of the TM's, and you will probably find the problem.
    "Curse your sudden but inevitable betrayal!" - Wash

    1984 M1009
    1997 M101A3

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    Could be a lot of things. Yes, the light is supposed to be on when you start. Check the bulb first, it is part of the circuit, then read the sticky alternator thread up top and start checking voltages.

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    Thank You both for the quick reply. I will check the bulb in the morning.

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    Quote Originally Posted by cpf240 View Post
    the GEN 2 bulb is 24v while GEN 1 is 12v.
    CFP240 Are you sure? I thought that Gen 2 is standard 194 bulb and gen 1 is standard 168 bulb?

    The generators only put out 12v, not 24.
    Last edited by Ken_86gt; 01-09-2013 at 22:06.

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    Moderator Warthog's Avatar
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    Gen2 is a 194 and the GEN1 bulb is a 168. The difference is the wattage.

    The voltage thru the GEN2 bulb is 24v. The diffence in the bulb wattage allows them to have the same brightness.
    "We are all born ignorant.....but one must work hard to remain stupid" - Benjamin Franklin

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    4 Star General cpf240's Avatar
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    Quote Originally Posted by Ken_86gt View Post
    CFP240 Are you sure? I thought that Gen 2 is standard 194 bulb and gen 1 is standard 168 bulb?

    The generators only put out 12v, not 24.
    I should have been more specific, as Warthog was. Yes, both alts put out only 12v, but GEN 2 is using the 12v output of GEN 1 as its ground reference. Which is why GEN 2 *MUST* be an isolated-ground alternator. So, when measured from chassis ground to output of GEN 2, you get 24v. GEN 2 using the output of GEN 1 as its ground reference is why GEN 2's exciter circuit needs 24v, not 12v like GEN 1.
    "Curse your sudden but inevitable betrayal!" - Wash

    1984 M1009
    1997 M101A3

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    This is a 5 year old thread but the information is still good to know. Very helpful information here. I was looking at it because of my current issues with a customers truck. I was never aware of the cluster bulbs being different. I used 194 bulbs on all the bulbs. Never knew it would matter. Learn something new every day. Just never bothered to look. 194 are abundant bulbs and I have many as that is the predecessor of the LED clearance lamp that we do not use anymore. I removed them from discontinued clearance lamps and recycled the lamps base and lenses. I know the 194 bulb is 12 volt but it must also be able to run on 24 volt. That explains the heat in that socket when the key is left on a long time. Merry Christmas.
    To argue with a person who has renounced the use of reason is like administering medicine to the dead. Thomas Paine: Founding Father Quote.

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