Light switch test confirm.

Discussion topics on Willys Overland M series vehicles

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4x4M38
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Post by 4x4M38 »

Just remember unless you are looking
at the two early Bendix switches the newer
ones have internal breakers.
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DC
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Resister in later switches

Post by DC »

I have a couple questions regarding the 3 position light switch, forgive me if this is the wrong spot to ask it. This is for My m38a1
1. What size is the resister/breaker in the switch?

2. How many amps is the switch designed to handle? In other words, how many amps flows through the switch and resister to run the lights on 24v?

I finally understand the increase amperage requirements with 12 volts, I think. In order to deliver the same brightness (watts) in 12 v as the 24 v lights, will require increase amperage. Thus the almost doubling in amps to run the 12v lights. Although, I came up with a hair brained idea to test on paper. Using LED bulbs, which draw a fraction of the amps required to produce the same amount of light, thus lower amps flowing through the switch? For example a 30 watt incandescent light bulb equivalent LED is only 3.6 watts. So it should take significantly less amps to light up the LED bulbs.
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wesk
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Post by wesk »

The CB rating in the latest copy of the milspec for that switch is 20Amps. S as long as your total (max # lamps on at the same time) is less than 20 amps the switch will handle it.

To find these MILSPECS just locate the FSC (5930 for this switch) in your parts manuals and go to the MILSPEC page Everyspec.com and search for FSC: 5930. There you can download the old original spec MS51113 and the current version MIL-PRF-11021H . These will answer any questions you may have about the engineering of the switch.

http://everyspec.com/
here's the old spec MS51113: http://everyspec.com/MS-Specs/MS5/MS51113C_18847/

here's the latest version MIL-PRF-11021H: http://everyspec.com/MIL-PRF/MIL-PRF-01 ... 21H_49853/
Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100

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jeeperjoe
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Post by jeeperjoe »

Jeff_Lee wrote: Not pretty:
Image

I took one of the late model switches apart and it also looked like this. Getting it apart was difficult enough but there was NO hope for the internals. :-(
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DC
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Thanks Wes

Post by DC »

Thanks Wes, if I have luck with the LED bulbs, on 12v, I'll post in a new forum, with my solutions, and calculations. I can post where I find working LED bulb replacements. I think I found an online source rated to work from 9v to 30v. Will let everyone know what I figure out. Thanks for the info.
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