Signal lights, hazard and brake lights don’t work

[Unimog66]

Hi
just bought a 1996 m1084, the signal , hazard and brake lights don’t work, can anyone give me tips on where to check, they worked the first day but don’t work now. i am new to these trucks and don’t know a lot about them. Maybe someone has a little video on the 3 levers where to position them
thanks

 

[GeneralDisorder]

Military trucks in general start out in light discipline mode by default where nothing works till you select either service drive or park. Once you turn on the headlights all the other systems will function. With the headlights switch in "off" NOTHING in the lighting system will function.

 

[Ronmar]

Yep, select service drive, by raising the short lock lever to allow you to rotate the top lever to the service drive position. You also do not have any brake lights until you do this…

 

[hike]

Welcome!

Here on the forum you will likely find what you need for this and other issues that may arise. First you may want to look in the TM section:
Forums/Technical Manuals/FMTV>

While not a TM for the M1084, the M1083 (and other A0 FMTV's) have a similar light switch. The TM_9-2320-366-10-X are operator manuals. If you look at TM_9-2320-366-10-1 the last entry in the contents may assist you.



Others here will be able to help much more.

Does your unit have the material handling crane?

 

[Unimog66]

Yep, select service drive, by raising the short lock lever to allow you to rotate the top lever to the service drive position. You also do not have any brake lights until you do this…

I did what you said and still don’t have any lights working except for the headlights, and parking lights

 

[Unimog66]

2nd photo

 

[hike]

Have you checked the flasher relay (PDP) and the brake light switch (pedal)? Schematics are at the back of certain TM's—

 

[Ronmar]

Well there are 2 brake-light switches in parallel, so I suspect the issue lies elsewhere. Sadly, the light circuit is the most complex/convoluted on the truck

lets start with just the brake circuit.

1. Do any relays in the panel energize when you step on the brake pedal? If so, which ones are activating? With engine off, ign on and air tanks full, stepping on the pedal you should be able to hear them, and feel them click to identify exactly which ones are activating. I am thinking there should be at least 4 relays, K6, K10, K30 and K31…

 

[G744]

Do the 4-way hazards work?

In any case, it is usually the turn signal switch failing, as it routes all circuits having to do with signals.

If the switch is bad, there are many Asian copies out there, and they are problematic.

Search for a turn switch unit from Nartron, they are the best and have not been copied.

This is the good one, but these guys are sold out. I'd search eBay.

HMMWV Nartron Self Cancelling Signal Switch Assembly 12447083 1030012 6220-01-408-7785

HMMWV Nartron Self Cancelling Signal Switch Assembly 12447083 1030012 6220-01-408-7785 New. Stored by US Military. No box. www.hummersurplusparts.com

www.hummersurplusparts.com

 

[GeneralDisorder]

This is the good one, but these guys are sold out. I'd search eBay.

HMMWV Nartron Self Cancelling Signal Switch Assembly 12447083 1030012 6220-01-408-7785

HMMWV Nartron Self Cancelling Signal Switch Assembly 12447083 1030012 6220-01-408-7785 New. Stored by US Military. No box. www.hummersurplusparts.com

www.hummersurplusparts.com

FMTV's don't use this switch. They use a German column switch that has integrated wiper, washer, and horn controls.

FMTV LMTV MRAP Turn Signal Switch 6220-01-376-3676 12417597 M1078, M10

backorder, expect begin of 2023 FMTV LMTV MRAP Turn Signal Switch 6220-01-376-3676 12417597 M1078, M1079, M1080

secoparts.net

 

[G744]

Ah, I stand corrected as I've never been in a FMTV.

 

[coachgeo]

So you giving up and going back to your 404 yet? .

you'll figure it out. look at fuse panel and see if you got the breakers in their for lights etc. They may have been robbed from the truck for other trucks. Happens.

 

[Ronmar]

Started this schematic a while back and finally finished it, condensed from the pages of schematics for the A0. Just the basic on-truck lighting, no blackout, rotating beacon, park or 24v commercial trailer circuits(its complex enough without all that)

 

[CallMeColt]

Are you sure they worked? Do you hear the relays clicking? The hazard switch is missing. If it was replaced with a single pole switch from another spot like it looks like it may have, it may not let any of the signal lights work properly. You need the proper hazard light switch hooked up for power to flow right. Chased this issue on a truck for a long time. Popped a new hazard light switch in & it all went away. Maybe there was a deeper issue as looking at the diagram, I don't think it should have mattered but it did.

 

[Ronmar]

Are you sure they worked? Do you hear the relays clicking? The hazard switch is missing. If it was replaced with a single pole switch from another spot like it looks like it may have, it may not let any of the signal lights work properly. You need the proper hazard light switch hooked up for power to flow right. Chased this issue on a truck for a long time. Popped a new hazard light switch in & it all went away. Maybe there was a deeper issue as looking at the diagram, I don't think it should have mattered but it did.

Yep, It does matter as the base power for the flasher module for use by the turnsignals is provided by the hazard normally closed contacts when in the hazard off position. When you select hazard on, it provides power from a different source, but one that still must be authorized by the light-switch in a non-blackout mode Via K09. K09 is called the hazard blackout override relay…