Dim headlights

[Victorkilo31]

So noticed yesterday headlights were a bit off. No low beams, brights had pass side brights, driver low. Fiddled around a bit today. Both bulbs are 24v, determined one has high beams burnt out. One had wrong wires in wrong spots which I fixed. Also fixed old broken plug end stuck in the head light housing. After this I got the lows to come on both lights and the one high beam light. However the lows are like dead battery dim. Connections seem solid, wires didn't flicker at all when moved around, batts are charged up. Lights are the same truck running or on batter power. Rest of the lights work nice and bright, even black out lights, the high beam light that works is definitely bright.
So I'm at a loss. I'm rebuilding my tool set or if have plugged a meter in to it tonight, it's a plan for the weekend getting one.
Now a couple questions. Does wires 17 and 18 matter which socket they are in? 16 matches up with the power in pretty easy, the others no idea.
Could the blown high beam be the problem?
I'm gonna try to find the ground for the headlights when I have better and check there, but with the highs working I'm at a loss

Suggestions welcome

Thanks

 

[MOOSERABBIT]

check the harness connection at the left front corner. mine was doing the same, connection was loose. cleaned, dielectric grease and has been good to go since.

 

[99nouns]

Was the low beams bright before and suddenly became low or did you just got the truck or lamps?

There are 2 different kind of head lights for this truck, one is military grade I think 100/120 hard to get and very expensive high beams can light up a football field, short life, than there is civilian grade 60/100 which looks like like they are not even on at night in low beams, available any parts store and cheap, lasts longer.

Numbers stand for illumination power I forgot the term.

 

[Victorkilo31]

QUOTE=MOOSERABBIT;2050357]check the harness connection at the left front corner. mine was doing the same, connection was loose. cleaned, dielectric grease and has been good to go since.[/QUOTE]

The one where the light harness plugs in from the hood? Checked it. It's nice and tight, all wires appear to be as well. Will check again to be sure

Was the low beams bright before and suddenly became low or did you just got the truck or lamps?

There are 2 different kind of head lights for this truck, one is military grade I think 100/120 hard to get and very expensive high beams can light up a football field, short life, than there is civilian grade 60/100 which looks like like they are not even on at night in low beams, available any parts store and cheap, lasts longer.

Numbers stand for illumination power I forgot the term.

Well when the problem started didn't have low beams, but when the truck had highs on the drivers side low beam would come on. It appeared to be a normalish low beam ( guessing on that cause it was day light outside) I'm fairly sure they are military grade bulbs, but I'll check again after work and run the numbers.

 

[papakb]

I keep reposting this reference page for military wiring so that new MV owners will understand how these things work. Here's the link: http://olive-drab.com/images/7070301_circuit_numbers_dolph.pdf

First off it isn't 16, 17, and 18. It's 17 = high beam lead, 18 = low beam lead, and 91 = headlight ground so yes, it does make a difference where the wires get connected. If you get your wiring wrong and get the 2 filaments in the lamp wired in series it will look like what your describing. In the HMMWV they give you multiple opportunities to screw up the wiring. There are the wires that come off the bulb itself and connect to the feedthrus in the lamp housing and the wiring in the harness that connect to the other side of the feedthrus. Be careful when plugging them in to make sure you get then connected to the right places. You want 17 to 17, 18 to 18, and 91 to 91. Interchange things and the lamps will either be dim or off.

Then they put a connector right at the end of the frame rail that connects the hood harness to the body harness that gets loose and corroded. Make sure that is clean and tight. Lastly they give you a pair of switches made by the lowest bidder (master light switch and dimmer switch) that are known high failure items,

With your multimeter check for voltage on wires 17 and 18 in both high and low beam modes to make sure you have voltage to the lamps. If you don't your back to the body connector and the switches. Also with your multimeter you can read the resistance of the lamp filaments to make sure they aren't burned out. With the multimeter in resistance read between wires 17 and 91 and them between 18 and 91. If you get readings in both positions the lamps are OK

Hope this helps,

Kurt

 

[Victorkilo31]

Thanks for the post. I missed it in my searching for solving this problem. I did get the right labels to the right wires on the lights, one side had 17 and 18 connected. I was wondering if connectors 17, and 18 on the high/low switch have designated spots. I know #16 does, the other two im not sure on. I'll be getting a meter either today or tomorrow. From a visual right now all connections appear clean and solid, but I'm gonna recheck again tonight

 

[papakb]

It won't hurt to give all of them a liberal dose of WD40 and even better would be a coating of Dow Corning DC4 silicon lubricant. It's available from places like Skygeek, Aircraft Spruce, and McMaster-Carr. I use it on all of my electrical connectors to exclude moisture and soften the rubber pieces.

 

[Victorkilo31]

It won't hurt to give all of them a liberal dose of WD40 and even better would be a coating of Dow Corning DC4 silicon lubricant. It's available from places like Skygeek, Aircraft Spruce, and McMaster-Carr. I use it on all of my electrical connectors to exclude moisture and soften the rubber pieces.

Yeah gonna see what I can find tonight for it when I get a meter and start taking some readings and narrow this down and get it fixed

 

[Victorkilo31]

Made some progress I think. Ran the meter after work and got no open lines, grounds are good, battery voltage consistent across 17 and 18 for power to the lights. Did notice that 17 and 18 are shorting somewhere though. Getting power from wire 17 and 18. I checked light socket 17 to 18 for grins caise eveything else seemed fine. Checked both side. From the couple schematics I found the two wires shouldn't touch anywhere correct? Doesn't make sense that they would but never hurts to ask. Gonna see if I can track it down in a few. I need a break lol

 

[Victorkilo31]

Ok. Done with this for a while. Pretty sure I've narrowed it to the bulbs. One was mislabeled (shocking I know) and the ground and I think wire 18 were wrong. That in turned caused other issues. So I'm stuck till I get new lights to make sure of things. Tempted to get some led since I'm replacing anyway

 

[papakb]

If your measuring the resistance of the lamp filaments you will have some continuity between wires 17 and 18 because they have a common ground on 91. The resistivity will be low but if you measure 17 to 91 you'll get one resistance reading then if you measure between 17 and 18 your reading should double because now your reading both filaments in series. This is normal. Sometimes you can look through the lens of the lamp and see the filaments if you hold it right.

With the wires disconnected from the lamp reading between wires 17 and 91 you should get about 24 volts with the master light switch on and the dimmer switch selected for high beams and 0 volts on wire 18. Change the dimmer switch and you should now get 24 volts on wire 18 to 91. If you are getting voltage on both wires at the same time then you have a short somewhere. It could be a bad dimmer switch or a pinched wire. The way the system works is the Master Light Switch sends power to the dimmer switch on wire 16 and then the dimmer sends power down wire 17 or 18 but not both at the same time.

Years ago I had mice build a nest behind the dimmer switch in my M151 that partially shorted the contacts together with gum wrappers.

The wiring diagrams are in the back of the -20-3 manual and the light circuit is the same for all variants of the HMMWV so any one will do.

 

[Victorkilo31]

Well had a couple minutes this morning. Went and checked voltages again.
With light bulbs removed and disconnected I get power from 17 and 18 to 91 ground
Also getting power between 17 and 18. I think next step I'm gonna try is disconnect the cannon plug between the hood and chassis, see if I can narrow it down a bit more now that heads clearer. At least that way I can figure out which side to look at.
Thanks again for all the help

 

[Victorkilo31]

Ok I think I've got 2 problems making me think it's one.
Did ohms check on lights and I think they are pretty much shot. Resistance reads pretty high or open.
I also think my dimmer switch might be bad. I pulled connector 17 off checked voltage at head light housing and it was off to ground. 17 and 18 no volts. 18 to ground I'm getting volts.
I also noticed polarity shifts too. Checking 17 and 18 on the cannon plug on the chassis side (pins a b and h) I'll get positive volts pin b to ground and negative pin a to ground.
I think I'm gonna go a head and get a replacement switch and headlamps, possible led upgrade while I'm at it.