My m998 brake lights stopped working ?

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Mikei998

New member
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Lewiston NY
My turn signals work , running lights work , head lights work but brake lights do not . Brake lights don’t come on when brake pedal is depressed. Where do I began to look ? Any info would be greatly appreciated! And the switch is not in blackout mode ...
 

donquijote

Member
134
3
18
Location
Louisiana
My turn signals work , running lights work , head lights work but brake lights do not . Brake lights don’t come on when brake pedal is depressed. Where do I began to look ? Any info would be greatly appreciated! And the switch is not in blackout mode ...
Check your brake light switch connected to your brake pedal. Its finicky if you have the old style.

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Wire Fox

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Steel Soldiers Supporter
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Indianapolis, Indiana
Check your brake light switch connected to your brake pedal. Its finicky if you have the old style.

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Agreed. Mine went out on me a few months ago and I was checking over all my connections, bulbs, and the like...then realized that the switch itself had loosened slightly and moved a tiny amount out if place. That was enough to cause total failure, so adjusting it until it was just short of contacting at-rest got it working again, then I torqued it properly so that it wouldn't move again. Very odd linkage setup, but it works when everything is set right...

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donquijote

Member
134
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18
Location
Louisiana
Yeah it's a PIA getting it dialed in. I always have someone behind while I adjust them saying whether they go on/off. I question some of the part design logic on these hmmwv's sometimes.

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papakb

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San Jose, Ca
After 3 of those useless switches I wired a normally closed switch in it's place and it turns on the brake lights as soon as the pedal leaves the stop. Part of the problem is there is no adjustment for free travel in the linkage and if you have properly functioning brakes they are stopping the truck as soon as the pedal leaves the home position. Then in combination with the short travel causing the switch contacts to arc pretty soon your stopping without brake lights.
 

donquijote

Member
134
3
18
Location
Louisiana
After 3 of those useless switches I wired a normally closed switch in it's place and it turns on the brake lights as soon as the pedal leaves the stop. Part of the problem is there is no adjustment for free travel in the linkage and if you have properly functioning brakes they are stopping the truck as soon as the pedal leaves the home position. Then in combination with the short travel causing the switch contacts to arc pretty soon your stopping without brake lights.
Got a part# for that NO switch? I'll do that from now on.

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papakb

Well-known member
1,427
46
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San Jose, Ca
It's normally closed, not normally open. That way the contacts close as soon as the brake pedal moves. Any NC switch will work as long as it's rated for 5 amps or higher and you can figure out how to mount it. Here's a link to the CPI switch that I used: https://www.cpi-nj.com/waterproof-switches/momentary-switches/

If you look at their limit switch section there are plenty of mounting options available.
 
Last edited:

donquijote

Member
134
3
18
Location
Louisiana
It's normally closed, not normally open. That way the contacts close as soon as the brake pedal moves. Any NC switch will work as long as it's rated for 5 amps or higher and you can figure out how to mount it. Here's a link to the CPI switch that I used: https://www.cpi-nj.com/waterproof-switches/momentary-switches/

If you look at their limit switch section there are plenty of mounting options available.
Thanks... did you use one of the B5 series standard momentary switches or the B2 mil-grade series? Yeah the limit switch section has some nice mounting options.
 

cajadao

New member
28
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3
Location
dallas/texas
I got the same problem once.
Found it doing a pre check before the inspection.
I started with the brake switch. Even when passing the continuity check, i could feel a bump when playing it by hand. I thought I found the issue. Replaced it, to find out it was not it.
The next circuit to work on was the turn signal switch. By checking the plugs D&E ( my right brake light was the problem), it failed on the continuity test.
Replaced it, problem solved.
 
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