left front headlight burning out frequently

[Z71]

I seem to have a problem with the left front headlight on my M109. For some reason, the low beam filament burns out on it quite often. I have gone through at least three replacement lights in the last two or threel years. The high beam works OK. The right headlight is fine.
The wiring seems good and connectors are clean. Could vibration be causing this? Why does only low beam go out? Is there anything I can do to fix this problem?

 

[hoop]

Clean and make sure you have a good ground wire.

 

[gimpyrobb]

What rpm are you idling at? The lower end RPMs will shake it to death, I keep mine up near 850-900.

 

[197thhhc]

 

[Danl]

Danl M915A1

Try adding a Wire to the ground post on the light, and ground it to the truck close to the light, or replace entire wire. try the Quick fix frist if it works than you know the real ground wire is breaking up and you decide what to do with it. If you know how to use ET Tester you could test the real wire and see what it has for continuty, but you will need to know the location of both ends The Quick ground is easyer

 

[rchalmers3]

I don't see how a bad ground could cause the bulb to burn out. A poor ground reduces current flow. As in a headlight that is dim or hardly on at all.

The things that burn out filaments are vibration and excessive current flow. I would look at those things first.

Rick

 

[wilfreeman]

Not trying to hijack your thread - just a comment. I had (might still have) the same problem with my M38a1. I have gone through 1 new Wagner bulb and a used bulb on the same side (right), and the high beam on the left side on one bulb once. I have a new wiring harness installed. After the right side bulb burnt out the last time, I added an engine to chassis ground and a 10 gauge ground from each light to the fender. I have been hesitant to try another bulb to see if that fixed the problem. The only other things I know to try are to check output volts and ground straight to the frame from the lights the next time I burn one out. Oh yeah, they don't vibrate much at idle (they shouldn't anyway - it its only a jeep, not a deuce!), so that shouldn't be the problem.

 

[doghead]

The rubber isolators get hard with time. You might try replacing those. Simply adjusting the idle most likely will help.

 

[fkowalski1942]

I don't see how a bad ground could cause the bulb to burn out. A poor ground reduces current flow. As in a headlight that is dim or hardly on at all.

The things that burn out filaments are vibration and excessive current flow. I would look at those things first.

Rick

My truck and my Jeep had this problem and i fixed it with a new ground wire, after that i never had this problem again. Its hard to understand but could happen.
When i had the problem, firstly i look for vibration and excessive current, i lost 6 headlights until i reached these simple fix.

Regards

 

[wilfreeman]

Not a cheap thing either, at @ $35 a pop!

 

[popacom]

Bad ground?????;

My two cents ain't worth two cents any more( thank you
China,Japan,Soviet etc.etc.etc) but as resistance increases, voltage
decreases.....the filaments in these sealed beams were designed
to operate at or around24-28 vdc. when your bad ground reduces
voltage below design parameters of the filament the life of said filament
suffers from it. I may be way off but those are my first reactions
when listening to what's happening. ...........popacom / Bill in Ky.

 

[Wildchild467]

What rpm are you idling at? The lower end RPMs will shake it to death, I keep mine up near 850-900.

Same here

 

[Wildchild467]

did you check what the voltage is at the batteries? if your generator voltage is set too high, that could contribute to the problem also.

 

[turbovr6jetta]

My two cents ain't worth two cents any more( thank you
China,Japan,Soviet etc.etc.etc) but as resistance increases, voltage
decreases.....the filaments in these sealed beams were designed
to operate at or around24-28 vdc. when your bad ground reduces
voltage below design parameters of the filament the life of said filament
suffers from it. I may be way off but those are my first reactions
when listening to what's happening. ...........popacom / Bill in Ky.

Heck, my 2 cents are worth so little I **** near have to pay to get rid of them. However I fully agree with the ground at least being a possibility. It was also my first thought

 

[m816]

You have a bad ground.Plain and simple. It could be a broken wire or a pinched wire or a loose connection. But it is still a bad ground and it is on the left side 'cause it is only affecting the left side light. Good Luck

 

[wpzimmer]

A bad ground or a bad hot lead (intermittent in both cases assumed) causes the headlamp to go on and off. Sometimes so quickly that it is not obvious to the eye. Tungsten filaments draw a lot of current when switching on from a cold or semi-cold state and this places a lot of stress on the filament, both thermally and magnetically. Weak spots in the filament (the wire is not completely uniform after a few operating cycles) will act like a fuse and blow out. Good, sound wiring if important!!

Also, Doghead is right. These trucks vibrate alot and the rubber isolators on the headlight bucket get hard with age or break resulting in much freedom of movement. McMaster-Carr sells a suitable replacement for the rubber isolators.
Also check for looseness in the grill mounting hardware. Grills move quite a bit when the mountings get loose or holes enlarge from corrosion or movement. LED headlamps are a good deal more resistant to vibration but still need sound wiring. Also are still quite pricey.

Another thought: Check your charging system voltage with a reliable meter. A few volts too high can cause greatly shortened lamp life.

 

[Z71]

did you check what the voltage is at the batteries? if your generator voltage is set too high, that could contribute to the problem also.

Yes, I did. the charging voltage is adjusted to about 27.5 Volts I think.

 

[Z71]

Same here

Mine idles around 800 RPMs.

 

[Z71]

You have a bad ground.Plain and simple. It could be a broken wire or a pinched wire or a loose connection. But it is still a bad ground and it is on the left side 'cause it is only affecting the left side light. Good Luck

Ok, I will check the ground and see if anything is loose or corroded. But as mentioned before, bad ground usually causes the light to not work, not to burn out.

 

[Z71]

A bad ground or a bad hot lead (intermittent in both cases assumed) causes the headlamp to go on and off. Sometimes so quickly that it is not obvious to the eye. Tungsten filaments draw a lot of current when switching on from a cold or semi-cold state and this places a lot of stress on the filament, both thermally and magnetically. Weak spots in the filament (the wire is not completely uniform after a few operating cycles) will act like a fuse and blow out. Good, sound wiring if important!!

Also, Doghead is right. These trucks vibrate alot and the rubber isolators on the headlight bucket get hard with age or break resulting in much freedom of movement. McMaster-Carr sells a suitable replacement for the rubber isolators.
Also check for looseness in the grill mounting hardware. Grills move quite a bit when the mountings get loose or holes enlarge from corrosion or movement. LED headlamps are a good deal more resistant to vibration but still need sound wiring. Also are still quite pricey.

Another thought: Check your charging system voltage with a reliable meter. A few volts too high can cause greatly shortened lamp life.

What do you recommend for the charging voltage? I will check the grill connections for tightness.