HMMWV no lights at all ???

[Swatpilot]

I’m having the same issue with no lights on a new truck I just got. It had the push button light switch and I replaced it due to everything I have heard about them. Still no lights. Will be checking the 15a wire tomorrow and maybe disconnect the pcg if there is no power on the wire.

 

[Mogman]

I’m having the same issue with no lights on a new truck I just got. It had the push button light switch and I replaced it due to everything I have heard about them. Still no lights. Will be checking the 15a wire tomorrow and maybe disconnect the pcg if there is no power on the wire.

Welcome to the SS forum!!

 

[Mogman]

Remember to always disconnect the batteries when installing or removing the connectors on the PCB/EESS box.
And as stated before if you bought an aftermarket switch that could also be your problem.

 

[thoner7]

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... .

All my lights went out at the same time with a click or pop. I can jump the wires to get my headlights to turn on. So I assume it’s my switch and my fuse popped.

I can replace the light tri switch easy enough, but why would my fuse have blown? Do these just have a shelf life or what?

 

[Mogman]

All my lights went out at the same time with a click or pop. I can jump the wires to get my headlights to turn on. So I assume it’s my switch and my fuse popped.

I can replace the light tri switch easy enough, but why would my fuse have blown? Do these just have a shelf life or what?

It does not have a fuse, the light switch has an auto reset breaker.

 

[thoner7]

It does not have a fuse, the light switch has an auto reset breaker.

“Auto reset” — so what does that mean ?

 

[Mogman]

“Auto reset” — so what does that mean ?

It means when the short is removed it is supposed to automatically reset, there are so many Chinese knockoff electrical components out there and they are all crap unless you are sure you have a legitimate switch that could be the problem, also do you have a 400A alt? if so there is likely a short on the rear of the alt where the harness can rub on it.

 

[thoner7]

It means when the short is removed it is supposed to automatically reset, there are so many Chinese knockoff electrical components out there and they are all crap unless you are sure you have a legitimate switch that could be the problem, also do you have a 400A alt? if so there is likely a short on the rear of the alt where the harness can rub on it.

I got my truck from RWH so I believe it’s a legit and the original switch. The alternator was replaced with the 200 amp.

I did remove the front blackout light and electrical taped the wires up under the hood. That’s the only thing I could think of that I may have done.

 

[thoner7]

I had a chance to review the TM. It doesn’t mention anything about there being a short or looking for one. It just says to replace the switch if it’s broken…? I guess I’ll order one and hope for the best?

 

[thoner7]

It means when the short is removed it is supposed to automatically reset, there are so many Chinese knockoff electrical components out there and they are all crap unless you are sure you have a legitimate switch that could be the problem, also do you have a 400A alt? if so there is likely a short on the rear of the alt where the harness can rub on it.

Ugh. My new light switch also doesn’t work. So I must have a short somewheres.

Does anyone know how I could test for the line/fixture that would be shorted? There’s no procedure for this in the TMs.

Isn’t there a way to measure the resistance/ohms of a circuit ? Sorry I’m a novice with cars, but I’ve done that before to find a broken element on a water heater.