HMMWV no lights at all ???

[jcappeljr]

My m998 that I got from Govplanet has no lights anywhere,I replaced the headlight switch with 4 other switches,and replaced the turn signal switch.Does anyone know what wire is the supply wire to the switch ?Also the is 1 wire coming out of the headlight switch harness that is cut,but I cant find where it might go.Any help would be appreciated.Are there any fuses ?

 

[DatGuyC]

Wiring diagram:

View attachment M996-M997-Wiring-Diagrams.pdf

 

[jcappeljr]

Still haven't got the lights working.the above diagram is very hard to figure out.Does anyone know which # wire supplies power to the headlight switch..thanks.

 

[tim292stro]

Looks like #15A to pin F on the MLS plug, and pin F on the PCB.

Hint, print them out and tape them together.

 

[jcappeljr]

If anyone has any other suggestions on my problem ,let me know..thanks..

 

[tim292stro]

Have you measured the voltage to that pin at the MVLS connector? Just disconnect it from the switch and measure the voltage in relation to any hard metal surface (like a steering column bolt). With the PCB working correctly, it should show 24V approximately.

If there's no power at that pin, it's either your PCB or the harness.

If there is voltage present, it's possible your 3-lever switch is shot. There is a circuit breaker inside, and if they go bad you generally replace the whole switch. After that, you can start doing continuity tests on the switch itself to see if the internal contacts are good, and using a jumper wire from pin F to pin M to see if your headlights turn on - do it only for a short duration (3 seconds or less), without that circuit breaker in the MVLS if there is a fault (i.e. short to chassis ground), you could end up burning down your truck...

With all of your lights dead at the same time, it sounds like the circuit breaker though... .

 

[jcappeljr]

Thanks,Tim.

 

[jcappeljr]

Problem solved,,,No power at wire 15a,So I decided to change the pcb.I unhooked the batteries,unbolted the pcb and the last thing I went to unplug was the wire harness inside.It **** near fell off in my hand.I don't know how it even started and ran.I honestly believe someone unhooked a few things on this truck before I got it.When I first picked it up,I went to slave start it and discovered someone unhooked the ground wire to the slave adapter.I fixed that,it still would not turn over,discovered the start switch was a little loose.Fixed that it started right up.Then this issue were the connector to the pcb was hanging by 1 thread.Everything is good to go now,thanks for everyones help..

 

[tim292stro]

Glad you were able to figure it out - double bonus it was a "Free" fix

 

[gcbennet]

I had the same issue with having no lights. The common fault is bad grounds. They can make your humvee life miserable. After cleaning and preserving all of the grounds, then running through the troubleshooting guide in the TM i discovered corroded wires within the main cannon plug of the engine harness. The rubber had age cracked and over time moisture seeped in and destroyed the plug. Not directly related to my lights issue, yet equally problem-causing, i also found several wire splice repairs here and there that had either lost their electrical tape over time and corroded, or corroded unseen within the repair itself. Before spending lots of $$$ on swapping out parts hoping the problem goes away, everyone should utilize the troubleshooting guide first.

 

[tim292stro]

Corroded under hood connectors is a very comon HMMWV issue - both the PCB and Glow Plug controller suffer here...

 

[gcbennet]

I install all of my connectors with dialectric grease to keep moisture out. I also learned a hard lesson and added a coating to the top of the cannon plugs where the wires pass through the rubber to seal-off that potential point of moisture ingress as well.

 

[Formansr]

I just got my 1993 M998 last month and all working fine (including Lights) until tonight - it started up just fine and I turned on lights just fine as well but all the lights went out 3-4 minutes later - no break lights either.

So - should I check the breaker first (and where would it be - some say behind the instrument panel)) and I'm also not sure how to locate the troubleshooting guide you mention that's in the TM.

Any help or suggestions appreciated.

 

[Wire Fox]

I just got my 1993 M998 last month and all working fine (including Lights) until tonight - it started up just fine and I turned on lights just fine as well but all the lights went out 3-4 minutes later - no break lights either.

So - should I check the breaker first (and where would it be - some say behind the instrument panel)) and I'm also not sure how to locate the troubleshooting guide you mention that's in the TM.

Any help or suggestions appreciated.

Volume 1 of the -20 TM has a troubleshotting guide for a lot of systems in the vehicle. In the TM repository on this website, there's also an "A1 Troubleshooting Guide" that is also pretty useful and has more pretty pictures. The circuit breakers on an original or A1 HMMWV are solely behind the dash, on the steering column. Lay awkwardly on the floor and look straight up and you'll see them on a gusset, both of them facing toward the center of the vehicle. Before you go plugging and unplugging wire, go ahead and disconnect the ground cable from the battery series and then start looking around for frayed wires or corroded connectors. In your situation, it sounds like you either have an intermittant connection or a poor connection that is heating up and going over-current for the circuit breaker. I'd start by looking around the connector for the master light switch and the turn signal switch, as they both have a lot of the light circuitry pass through them.

 

[Formansr]

Thank you - great suggestions.

BTW - I'm having trouble downloading the TM on this website - not sure why but will keep trying.

Have a great day.

Steve

 

[drowens1]

Does anyone know where I can locate the electrical control box on my Humvee? I just got it running but can't get any lights to work. I would just like to begin at the source.

 

[1 Patriot-of-many]

Does anyone know where I can locate the electrical control box on my Humvee? I just got it running but can't get any lights to work. I would just like to begin at the source.

I would start with troubleshooting the triswitch. I'm not sure what you mean by electrical control box, but if you're taking about the protective control box, it's under the dash where your left foot would be up the firewall on the inside. Page 202 of TM 9-2320-280-20-2

Just remember anytime you are monkeying with the electrical system, disconnect your negative ground from the battery. That box costs $600 and it's very prone to being shorted out.

Since this is your first post I'm assuming you know how to operate the triswitch? If not read the operating TM for the vehicle.

 

[1 Patriot-of-many]

Does anyone know where I can locate the electrical control box on my Humvee? I just got it running but can't get any lights to work. I would just like to begin at the source.

This might help you.

 

[Beardedpastor]

I need some assistance. I have read all this thread and don’t want to mess up or throw money at problem.
I lost all my lights. I unplugged the connector under dash that goes to PCB and 15a fell out of the connector. I put a meter on it and there is no power.
Where does 15a get power from?? Should it have power at this plug??

 

[Mogman]

15A is the main power feed to the light switch, it gets its power from pin F of the body side connector of the PCB/EESS box.
It should be hot all the time.