m151a2 headlight question

1959 - 1978, M151, M151A1, M151A2, Technical questions and discussions, regarding anything related to the M151.
brent
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m151a2 headlight question

Post by brent » Thu Jan 26, 2006 5:18 pm

just picked up a nice mutt. one headlight did not work. so I ordered a new one from rapco. no matter how I try to hook it u p. i does not light up. what do I need to look for on this? just thought of swapping headlights since the one side work. anyways thanks for your thoughts. brent
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Mark Warner
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Post by Mark Warner » Thu Jan 26, 2006 6:55 pm

Do your wires have the aluminum number tags attached?

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Post by ccandgc » Thu Jan 26, 2006 7:40 pm

had a similar problem, it turned out to be the 3 lever switch...problem gone...

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lights

Post by svramselaar » Fri Jan 27, 2006 2:07 am

hello

there are allu tags with nr on it on the wire`s
on the outsite of the lightpot unther the hood are numbers stamped in the pot

nr 91 is the ground

it is on the left side grounded at the generator ground cable
(same bold)
at the right it is in the inside of the right fender grounded

nr 17 is the high beam
nr 18 is the low beam


the lights nr 17/18 come from the foot dimmer high low beam
the 3 lever switch only turns them on gets power to nr 16 dimmer switch


i think ground is not ok

greetings george
1976 ? M 151 A2 AMG MUTT lost in acsedent
1978 M 416 A1 ( parkhurst ) trailer
1970 m151 A2 FORD BUDD tub
1957 Volvo sugga radio truck
M 274 mule HOME MADE MULE

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Louie
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Post by Louie » Fri Jan 27, 2006 9:31 am

I agree with George, Check the ground. If you have a 24 volt test lamp, you can check #17 and #18 for power to ground while having someone work the high/low beam switch :idea: . Do not use the ground from the headlight for the test light, use an engine or chassis ground.

Good Luck,
Louie,
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brent
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Post by brent » Fri Jan 27, 2006 7:11 pm

I will have to check the ground. because I pulled the light on the other side. then new one worked on that side. but neither of them work on the drivers side. must be a ground. cause it is not the bulb. wish i had a 24 volt tester. I have an ohm meter would that work? brent
Brent Frank
Pinehurst Idaho
ford gpw 19466
DOD. 27Apr1942

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Louie
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Post by Louie » Fri Jan 27, 2006 7:35 pm

Hi Brent,
The ohmmeter set to dc volts would work, however you can get a false reading on a poor connection. For instance, a weak ground would allow you to still read 24 volts. This is because the ohmeter (set to volts) draws very little current, and can "be fooled" into thinking you have a good connection. As soon as you try to draw any current (like lighting up the headlight or a test lamp) is when the trouble would show up. :idea:

As far as the test lamp, I went to napa and purchased a 12 test light for 5 bucks, and then changed out the bulb with a 24 volt one. They also carry the 24 volt bulbs. The test light I have uses the same bayonet lamp that our mutts use in the dash lighting and turn signal indicator. :idea:

You could also try as a test ,attaching a temporary wire (like an aligator clip test lead) to ground and to the headlight bulb ground.. If you are not sure which wire that is pull the one you think is the ground from the headlight, and use your test ground wire direct to the bulb. You will not hurt anything this way. If you accidently connected your ground to the hot wire to the bulb, you will be testing the circuit breaker in your mutt (not good). :oops: So disconnect the wire from the bulb before you ground it. :idea:

Good Luck,
Louie,
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Post by Travis » Sat Jan 28, 2006 4:03 pm

set your meter to the ohm scale. insert the probe into the end of the ground wire and the other probe to a known good ground. You should have less than 1 ohm of resistance. you can check continuity by disconecting both ends of the wire and checking the resistance. if you have an open you will read infinite resistance.
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Post by brent » Sat Jan 28, 2006 6:38 pm

I will check itout in a few days. thanks for all your help. is there a seperate ground wire in this circut? or is one of the plugs go to a frame ground? it is only that one side the other light works. so It must be in the ground. thanks again you guy's. my mutt is really fun and roomy to drive. brent
Brent Frank
Pinehurst Idaho
ford gpw 19466
DOD. 27Apr1942

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headlight

Post by svramselaar » Sun Jan 29, 2006 1:46 am

hello

if the light is build in correct
to test ground take lose wire nr 91 from the light steel pot (housing)
outside
put a other wire on the pot on the open nr 91
NOT ON THE WIRE
put this wire on a good point for ground ??

if you get a ohm meter it is not for testing a bad ground working
you dont get amps moving trow the wire or to the ground
do it like louie with a test probe

go for a wire plan to

www.tnjmurray.com/M151A2_wire_1.jpg front half

www.tnjmurray.com/M151A2_wire_2.jpg rear half

let us know if it is the left or right headlight

see also my message above for ground points

greetings george
1976 ? M 151 A2 AMG MUTT lost in acsedent
1978 M 416 A1 ( parkhurst ) trailer
1970 m151 A2 FORD BUDD tub
1957 Volvo sugga radio truck
M 274 mule HOME MADE MULE

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Post by Travis » Sun Jan 29, 2006 9:03 am

An ohm meter is made to check resistance. A volt meter measures voltage. An amp meter measures current. A low resistance reading means that you have a good connection while a high reading is an indincation of a poor connection. Since air is a very poor conductor an open circuit will show infinite or full scale reading. On a digital meter this will usually be indicated by -OL-. To check a connection of any kind you need to check the resisance because as resistance increases current decreases. Current ( I ) x resistance ( R ) = voltage ( V ). Example 24v / 100 ohm = .24 amp. 24v / 1000 ohm = .024 amp. As the resistance increases more energy is converted into heat and therefore more current is needed to maintain the desired voltage. An easy way to remember the formula is to draw a circle with a horizontal line thru the middile of the circle and a vertical line that extends downward from the middle of the horizontal line to the bottom of the circle. In the space above the horizontal line place the letter V (volts ). In the lower left space place the letter I (current ). In the lower right space place the letter R (resistance). To use the aid , just cover the quantity that you want to find and perform the muliplication or divison indicated. While a test light is a quick and easy way to see if you have enough voltage & current to light that particular bulb it does not tell you if you have excessive current drain or if the wire will carry the load (resistance) that you are going to put on it. For instance a 24 volt 20 watt bulb would draw .833 amp while a 24 volt 100 watt bulb will draw 4.16 amps. I = P (watt ) / V.
Travis.

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Post by DannyCop » Sun Jan 29, 2006 9:25 am

Travis, my gosh, great explanation but you nearly caused my head to explode. LOL

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Re: headlight

Post by Travis » Sun Jan 29, 2006 9:34 am

[if you get a ohm meter it is not for testing a bad ground working
you dont get amps moving trow the wire or to the d]

An inadequte ground will have current flowing thru it. Put a small wire from the neg to a ground point and place a load on the circuit and the ground wire will heat up due to incressed resistance and more current flowing thru the ground conductor in an effort to mantian the desired voltage. A bad connection is the same as putting a smaller wire in the ground path because you are decressing the surface area of the conductor at that point. If you have an open gound circuit then there is no current flow.
Travis.

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Post by Travis » Sun Jan 29, 2006 9:41 am

Thanks Danny,
It did kind of put a strain on my old brain to put it in writting that might make a little sense lol:.
Travis.

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Headlight

Post by Ed Funchess » Fri Feb 10, 2006 1:52 pm

I do love George's posts from Holland-svramselaar. The explanations are just perfect and are right there if we Yanks could just learn to rearrange our verbs and adverbs and with a little creativity on the nouns. I blame the Democrats. George, you are the man. 91 is 16 upside down. You need to come over to the East Coast Rally.

I have to say this. I am no electrician, and do not understand it at all. Smart people have tried to explain voltage and current and amps and joules and lumens, etc, etc, to me as long as I can remember--I like the theoretical example they all use. Think of it as water going through pipes and valves, etc. Well, I know that aint right, because it aint like water. I remember when I was about 4 years old sticking my daddys Oldsmobile car key in a wall socket, and the reaction I got out of it was not anything like water. it was an orange ball and the only water involved was running down my leg. I am still dislexic from the experience, and probably some other things I am not consciously aware of, but would surface under hypnosis.

Luris(Louie) had the simplest solution. go get any el-cheapo test light probe and put one of the small dash panel bulbs in it instead of the 12v that comes in it. Then, you can have LIGHT. Where there is voltage, there is light. Where there is no voltage, there is no light. That is a truly indespensable item when working on electrical malfunctions on these Mutts.
Ed
Never be afraid to try something new. Remember that amateurs built the ark. Professionals built the Titanic.


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