Passenger side headlight, short

[Ajax MD]

This problem involves the OEM incandescent bulbs. I am NOT running LED's anywhere in this truck except for the gauge illuminators.

I observed my passenger headlight low beam not working.
I grabbed a spare headlight bulb and it promptly smoked the low beam again. Ok, the passenger low beam power wire is shorting to ground somewhere.

I grabbed my meter and tested for connectivity between plug #18 (low beam) of the headlight bucket and various metal points on the truck with the headlight combination switch OFF. Nothing, no short. With the switch ON, there is connectivity and there should be because wire #91 is ground and that's how the circuit completes.

All other lights on the truck work perfectly. What am I missing? Could it be the high/dim foot switch? Could it be the combination switch?

 

[kendelrio]

This problem involves the OEM incandescent bulbs. I am NOT running LED's anywhere in this truck except for the gauge illuminators.

I observed my passenger headlight low beam not working.
I grabbed a spare headlight bulb and it promptly smoked the low beam again. Ok, the passenger low beam power wire is shorting to ground somewhere.

I grabbed my meter and tested for connectivity between plug #18 (low beam) of the headlight bucket and various metal points on the truck with the headlight combination switch OFF. Nothing, no short. With the switch ON, there is connectivity and there should be because wire #91 is ground and that's how the circuit completes.

All other lights on the truck work perfectly. What am I missing? Could it be the high/dim foot switch? Could it be the combination switch?

If there is no short "before" the switch, then there has to be one "after" the switch. Have you checked continuity when you have low beam on vs high beam? Your bright switch is the only commonality between the two. That's where I would start.

 

[Ajax MD]

If there is no short "before" the switch, then there has to be one "after" the switch. Have you checked continuity when you have low beam on vs high beam? Your bright switch is the only commonality between the two. That's where I would start.

With power OFF, I have turned the combo switch to "service drive" and activated the high beam foot switch. There is continuity between all three pins in the headlight bucket. That seems correct to me because I think both beams are on when in "high beam." ...aren't they?

 

[Ajax MD]

Wait, according to the diagram that's not correct. It's either/or not "both." Maybe I've found the problem. Let me run out and check again.

 

[Ajax MD]

Ok, in addition to the meter I rigged a test light. Something between the headlight buckets and the hi/low switch is definitely wrong. It may be the switch.

With both headlights removed, using the test light on one bucket at a time:

- In "low" the passenger low beam (#1 lights the test light. The driver's side does not work. (Remember, the original problem is the passenger low beam blows out when both bulbs are installed)

17 & 18 are common to both buckets. I've traced the harness back to the foot switch and nothing is chafed or pinched. Can I simply remove the foot switch and check connectivity between the 3 terminals?

 

[kendelrio]

Ok, in addition to the meter I rigged a test light. Something between the headlight buckets and the hi/low switch is definitely wrong. It may be the switch.

With both headlights removed, using the test light on one bucket at a time:

- In "low" the passenger low beam (#1 lights the test light. The driver's side does not work. (Remember, the original problem is the passenger low beam blows out when both bulbs are installed)

17 & 18 are common to both buckets. I've traced the harness back to the foot switch and nothing is chafed or pinched. Can I simply remove the foot switch and check connectivity between the 3 terminals?

Can you shoot me the page/diagram numbers for the light circuit? Offshore and its a PITA using my phone.

Oh, and you're in the -10, right?

 

[kendelrio]

OK bud, my TMs didn't have the "Fold out" section of the wiring diagrams, but I found them. Here they are... these are .jpg for the sake of uploading. If you'd like to get a link to all of my tm pdfs, PM me your email Addy.

 

[Ajax MD]

It's ok, I found the problem. (I was using the big wiring diagram out of the -20) This is an M813.

Some jackwagon swapped 91 and 17 on back of the DRIVER's headlight bucket.
Apparently someone was clever and figured out that if you swap the same wires inside the PASSENGER bucket, the lights will work.
I did not pay attention when I disconnected the wires from the burned out bulb. (Why would I? Everything is labeled).
So I connected the wires correctly, causing a short between the headlights.

I've been driving this truck for 3 years and the headlights have always worked. That's the only explanation I can come up with.

So, I corrected the wiring malfunction on the back of the driver's headlight bucket and now everything works properly.

 

[kendelrio]

It's ok, I found the problem. (I was using the big wiring diagram out of the -20) This is an M813.

Some jackwagon swapped 91 and 17 on back of the DRIVER's headlight bucket.
Apparently someone was clever and figured out that if you swap the same wires inside the PASSENGER bucket, the lights will work.
I did not pay attention when I disconnected the wires from the burned out bulb. (Why would I? Everything is labeled).
So I connected the wires correctly, causing a short between the headlights.

I've been driving this truck for 3 years and the headlights have always worked. That's the only explanation I can come up with.

So, I corrected the wiring malfunction on the back of the driver's headlight bucket and now everything works properly.

Awesome! Thanks for the followup!!!

 

[US6x4]

Yes, thanks for the follow-up. There are too many issues in threads left open-ended without the solution being posted.

 

[Blizken]

It's ok, I found the problem. (I was using the big wiring diagram out of the -20) This is an M813.

Some jackwagon swapped 91 and 17 on back of the DRIVER's headlight bucket.
Apparently someone was clever and figured out that if you swap the same wires inside the PASSENGER bucket, the lights will work.
I did not pay attention when I disconnected the wires from the burned out bulb. (Why would I? Everything is labeled).
So I connected the wires correctly, causing a short between the headlights.

I've been driving this truck for 3 years and the headlights have always worked. That's the only explanation I can come up with.

So, I corrected the wiring malfunction on the back of the driver's headlight bucket and now everything works properly.

Hey Guys,

I am having a similar problem and hope you guys can chime in.
HMMWV M1123 A2.

The OEM pass side lamp dim-did not work but BRIGHTS BULB WORKED. Also the pass amber running lamp doesn't work and may be related(?) if its power is downstream from the dims.

I replaced the OEM array lamp with the plug and play LED array on both drive and pass.

Headlight Universal for Wheeled Vehicles 24 Volt LED Plug and Play Hea

These are true plug and play oem style headlights (single or pair) for your military humvee. Works with all models of military humvee. Note: real oem rubber shell connectors such as on this headlight, do not require an adapter to make them function with your vehicle. Adapters are susceptible to...

www.federalmilitaryparts.com

Drive side all good. Worked with both dim/bright with both OEM lamp and LED lamp.

Replaced pass lamp assembly with LED lamp.
Same problem as with OEM. Brights come on but no dims.

I am assuming I should just put the meter on "18"?

Looking for some plans of action here.

Thanks in advance.

 

[Blizken]

Hey Guys,

I am having a similar problem and hope you guys can chime in.
HMMWV M1123 A2.

The OEM pass side lamp dim-did not work but BRIGHTS BULB WORKED. Also the pass amber running lamp doesn't work and may be related(?) if its power is downstream from the dims.

I replaced the OEM array lamp with the plug and play LED array on both drive and pass.

Headlight Universal for Wheeled Vehicles 24 Volt LED Plug and Play Hea

These are true plug and play oem style headlights (single or pair) for your military humvee. Works with all models of military humvee. Note: real oem rubber shell connectors such as on this headlight, do not require an adapter to make them function with your vehicle. Adapters are susceptible to...

www.federalmilitaryparts.com

Drive side all good. Worked with both dim/bright with both OEM lamp and LED lamp.

Replaced pass lamp assembly with LED lamp.
Same problem as with OEM. Brights come on but no dims.

I am assuming I should just put the meter on "18"?

Looking for some plans of action here.

Thanks in advance.

Well that was fast and weird.
Solved.
I hooked the meter up and everything showed 24v on 17 and 18.
Plugged the lamp back in and it all works-including the amber.
No clue how or why but, I will take it.

 

[kendelrio]

Well that was fast and weird.
Solved.
I hooked the meter up and everything showed 24v on 17 and 18.
Plugged the lamp back in and it all works-including the amber.
No clue how or why but, I will take it.

That's why I call the electrical theory "PFM". Pretty Freaking Magical.

Glad it fixed.

 

[Blizken]

That's why I call the electrical theory "PFM". Pretty Freaking Magical.

Glad it fixed.

A true Miracle Of Science!

 

[G744]

Probably an intermittent ground on wire 91. It will let both filaments light dimly on one or the other dimmer switch position. Fiddling with it may have got a ground going OK.

DG