M38 12v Amperage question

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stiknruddr
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M38 12v Amperage question

Post by stiknruddr » Sat Dec 23, 2017 3:22 pm

I had to rewire the War Pig used a nos harness and put a 1 wire 12v alternator on it. Converted all lights to 12v. Used aircraft 15 amp circuit breaker as main cb. Used 12 gauge wire to the CB. Using later one plug light switch. After 20 minutes of operation it trips the 15 amp breaker which gets hot. Any advice on making it work? Seems 2 headlights and the tail lights should be ok on 15 amp cb.


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Re: M38 12v Amperage question

Post by mdainsd » Thu Jan 04, 2018 3:42 pm

What headlight bulbs did you use?

If you used Halogen 100w you are already over the 15amps, just saying, need to know the loads involved.
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muttguru
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Re: M38 12v Amperage question

Post by muttguru » Sat Jan 06, 2018 2:18 am

Hello Stik,
did you have your 24v starter re-wound to 12v ? If yes, can you please let us know who did the re-wind?
Thanks
Ken
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stiknruddr
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Re: M38 12v Amperage question

Post by stiknruddr » Sun Jan 07, 2018 6:08 am

I used standard 12v headlights and the jeep came with a 12v starter. The light switch is causing other issues I’m looking into bypassing the internal cb and use a inline fuse. I think I’m going to run a bigger wire to the light switch

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1943Willysgpw
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Re: M38 12v Amperage question

Post by 1943Willysgpw » Sun Jan 07, 2018 6:56 am

That alternator is capable of supplying 42 to 63 amps depending on which 10si you purchased. I would think you will need to temporarily by pass the breaker and place an amp clamp on the B+ cable coming from the back of the alternator. With all loads on vehicle running, take a reading. As was stated earlier, you may have to either go with a larger breaker (depending on wire gauge) or get headlights with a lower rating. Voltage X amperage = wattage. P.S. if the wire gauge is too small, you run the risk of a melt down. You can find a chart on line that will tell you the amperage rating to length of wire you will need to carry amperage according to demands.
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1943Willysgpw
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Re: M38 12v Amperage question

Post by 1943Willysgpw » Sun Jan 07, 2018 7:07 am

Oh yeah, if you do not have an amp clamp, do not take an amperage reading through the multimeter. It only handles up to 10 amps. That is why the amp clamp connects through the voltage jack and common.
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1942 GPW 1871 DoD 2-27-42 Dallas Plant
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1942 GTB 136166 DoD 9-18-42
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Re: M38 12v Amperage question

Post by Wolfman » Mon Jan 08, 2018 5:26 am

I am a little confused.
Where did you place the circuit breaker in the system ??
In the one battery wire to the alternator ??
Not normally a breaker in that wire and with an alternator the wire should to be 10 gauge because of the output amperage the alternator is capable of producing.
You might get away with a12 gauge wire since the system does not have a very big load. Sounds like mainly lights. On initial start up, alternator out put will be high but settle down once the battery is excited.
A breaker would go in the circuits to the various components.
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