A2 M1123 - Troubleshooting Stop Lamp Switch

[Milcommoguy]

Do the turn signals work? both left and right, emergency flashers too? Brake lighting goes thru the turn signal switch, Those funky stop switches can be a problem. Connect the two switch wires together and see if the brake lights come on... steady and not flicken and a flashing.

Simple test, CAMO

 

[fpchief]

Yessir it all works....nice idea! I bet they do!! Will report back!

 

[86humv]

Those brake switches go bad internally..[ contacts ]...
The 1123 has the dual switch...mech. connected together...one for trans, one for brake.
I took some apart, and the brake side was bad internally...spring broke, and it flopped around.

 

[fpchief]

Yea, this one is the dual lever. It is bad so now to find the best price on one.

 

[fpchief]

Decided to take switch off truck and do the continuity check one more time.....

With it out of the truck, wife holding switch and moving the lever it will close the circuit at a little over halfway across entire throw of lever. Decided to out it back In truck and hand operated the lever and still wont work. Can switch be bad to where it still closes circuit but maybe not good enough to turn on lights?

 

[Milcommoguy]

Sounds to me you need to have wife work the switch when stopping the truck.

That test would make some sense showing closing of the contacts with an ohm meter (is that what you did?) BUT still may not be able to handle the current of a couple of incandescent lamps as in AMPS (is that what your running?) if the contacts are fried, intermittent and all the other things that could go pewewee. One could go down the rabbit hole, or at best chasing its tail.

In a previous post #21 did one connect the leads feeding the switch together (brake connection leads from wiring harness, the correct ones for the brake circuit not transmission if you have 4L80 set up)

Must have the lighting switch in the Stop Lights position, and test that the turn signal control allows for a flashing turn lamp (your choice left then right) with the stop switch leads connected together and note... one lamp STOP the other side / direction flashing. Any hookie - pokie here and could be the turn signal switch. Lots of switching contacts in that puppy.

Try this... Leave it loose and plug it all together. Have wife work the lever of the switch just like before. Run around back and shout out what you see.

If using LED lamps that shouldn't be a problem to get them to come on in STOP. TURNing and it's another storytime.

All term posted here are electrical, CAMO

 

[fpchief]

I did connect them together with a little jumper but they did not come on. There is a full 24vdc at I think wire #1....maybe #16.

Here is a caveat.....I have my turn signal switch off....took it off to replace the detents inside since it doesn't click like it should....would having it off have anything to do with the stop lights? Think I will put it back on to see.

 

[Milcommoguy]

AUHhhhhh YEA.

Pull my finger, CAMO

AND the other part of the switch releases the torque converter lock up. It is 12 volts. Screw up with voltage going in the wrong direction and it's AAMCO time.

 

[fpchief]

What part does the turn signal play in the stop lights? I know the blinker interrupts the stop light....so does that mean that the circuit goes from stop switch THROUGH the turn signal and then on to the tail lights? Just seems stop lights should work even if turn signal is there or not.

 

[Milcommoguy]

Hmmwv. Stop and turn lamps are the same bulb. Single contact with return on the shell. So... only one filament and it's the bright one used for you guessed it, STOP and TURN.

So the turn signal switch (and the magic inside and leave it at that) prioritizes how the lamp behaves if a turn is in effect or a stop and passes thru. Sure the flasher interrupts the light to flash but the turn switch interrupts the STOP for that direction and so it can flashes. Vise versa. more or less, just keep this thought.

Put it all back and note the operation.

I knew something was wacky with this incomplete story.

To learn more on how it works see >

And a little electricity, CAMO

 

[Mogman]

Just a comment, I wired my brake lights direct to the hot side of the light switch (through a fuse of course) and the turn signals to the ign. "run" lead (again through a fuse) these are too important to rely on remembering to turn on the light switch and will save the battery by not having to remember to turn the light switch off.

 

[86humv]

What part does the turn signal play in the stop lights? I know the blinker interrupts the stop light....so does that mean that the circuit goes from stop switch THROUGH the turn signal and then on to the tail lights? Just seems stop lights should work even if turn signal is there or not.

Power from light switch goes into turn switch at pin D and comes out to brake lights at pin c
So...switch has to be connected.

 

[Milcommoguy]

Just a comment, I wired my brake lights direct to the hot side of the light switch (through a fuse of course) and the turn signals to the ign. "run" lead (again through a fuse) these are too important to rely on remembering to turn on the light switch and will save the battery by not having to remember to turn the light switch off.

That's a good idea to modernize the lighting switch and having to remember to flip it on or off to go for a ride. The chance to save the batteries... YEP, but with my luck a TICKET for no STOP and TURN lights.

BUT... I am not so sure of your wiring schematic, as I roll it around in my pea sized brain is incorrect. Without any control logic (even a diode proper rating) I get the impression that the way you describe it, one could turn on the lights and back feed power to the run circuit of truck. So if truck was running and one turned ON the lights, one could NOT shut off the truck. Now than can't be good either. ither, or maybe it is?

Correct me if I got that logic wrong.

Driving a HMMWV is like no other, CAMO

 

[Mogman]

That's a good idea to modernize the lighting switch and having to remember to flip it on or off to go for a ride. The chance to save the batteries... YEP, but with my luck a TICKET for no STOP and TURN lights.

BUT... I am not so sure of your wiring schematic, as I roll it around in my pea sized brain is correct. Without any control logic (even a diode proper rating) I get the impression that the way you describe it, one could turn on the lights and back feed power to the run circuit of truck. So if truck was running and one turned ON the lights, one could NOT shut off the truck. Now than can't be good either. ither, or maybe it is?

Correct me if I got that logic wrong.

Driving a HMMWV is like no other, CAMO

OK I am sure I am going to get some hate from the purists but here goes.
At the light switch, 22A is the stop light feed to the turn signal switch, 75A and 75B are the stop light switch, and 15A is the main power feed to the light switch
So I cut 22A, and both 75A and 75B away from the light switch connector, connect 75B directly to 22A then connect 75A through a fuse to a tap on 15A
VOILA 24/7 brake lights
467A feeds the turn signals and horn, I cut it away from the light switch and connect it through a fuse to 29A the switched hot side of the master start switch, now you have switched turn signals and horn when in the run position, and no there is no chance for backfeed,

You could also tie 467A and 75A through a single fuse to 15A, then the turn signals including the 4 way flashers would be available with the ign. off, it is just not the way I did it.

(note the schematic shows 476A spliced and becoming 467B, turn signal and 26A, horn outside the light switch but as I remember 26A is connected inside the light switch connector and I had to cut it loose and tie 467 and 26A together at the fuse)

AND of course ALWAYS solder ALL connections and use jelled heat shrink when ever possible, crimp on connectors are for lawn mowers......
Also leave enough wire at the light switch when you cut them to always be able to reverse anything you do and seal all loose (cut) ends


This is how I did it, as you can see if you tie 467A to 75A and just use the single fuse the turn signals and 4 way flashers and horn will also be hot all the time, ignore the numbers on the turn signal switch, I did not feel like building a component from scratch and I left out H which is inconsequential to this mod.

Also do not "bury" the fuse in the dash so you can get to it if needed, a breaker could also be used, 10A should be plenty..

 

[Milcommoguy]

NO hate here,. just brotherly love.....from a distance.

So I got it now, that those wires have been removed / eliminated from the switch making the switch just a head light switch.

No fiddling with the "switch" to go for a ride. Turning truck to RUN position fires up the basic honk, stop and turn.

It does however messes with the overall black-out feature. Can't be blacked-out with the horn a honking and lights a flashing.

Still the chance of leaving the light switch in black-out, park, dash, or headlights on, draining the batteries.

Lots of ways to "skin the cat" ( hope that doesn't stir the PC cat crowd), CAMO

Black cats matter..............................

 

[Mogman]

NO hate here,. just brotherly love.....from a distance.

So I got it now, that those wires have been removed / eliminated from the switch making the switch just a head light switch.

No fiddling with the "switch" to go for a ride. Turning truck to RUN position fires up the basic honk, stop and turn.

It does however messes with the overall black-out feature. Can't be blacked-out with the horn a honking and lights a flashing.

Still the chance of leaving the light switch in black-out, park, dash, or headlights on, draining the batteries.

Lots of ways to "skin the cat" ( hope that doesn't stir the PC cat crowd), CAMO

Black cats matter..............................

View attachment 807691

I stopped running from the cops when I was a teenager (back when you could do that and live to talk about it, fun times for sure!) so I cannot see any real need for blackout.
I have a set of "interlocking safety switches" on the aux. panel I built between the door post and dash, I could wire one of those in for "JIC" LOL

My biggest fear is not a dead battery, it's forgetting and not having brake lights, I doubt there is a single HMMWV driver out there that can HONESTLY say they have NEVER forgotten and started out without brake lights.

 

[gestut]

For what it is worth... When I first got my HMMWV, the brake lights would not come on unless I had brake pushed all the way in. Problem was that by that time I was already at a complete stop so nobody behind me knew when I was slowing down to stop. For me it was a simple adjustment of the switch, it had been put in pushed all the way forward preventing it from engaging unless pedal was all the way in. I adjusted it all the way out then gradually pushed it in until lights shut off then tightened it up and no problems since.

I am having the same issue
I have to brake real hard for light's to come on or they wont come on. I almost got rear ended. Where is the adjustment on the switch. From reading above there is no adjustment?

 

[gestut]

Many of the switches are out of adjustment, the early switch just controls brake lights, the A2 lights and
torque converter unlock. I’ve had Adjust almost half the trucks I’ve receive as TC won’t unlock.
its a PITA to get spot on sometimes.

I have 1097 a2. So where is the adjustment for brake lights. I have to press real hard to come on. By then wheels are locked .

 

[papakb]

After farting around for weeks with trying to get that silly non-adjustable linkage switch to work I finally gave up and installed a sealed, normally closed switch in its place. Now whenever the brake pedal comes off of the stops the lights come on. Another option would be to install a tried and true pressure switch in the brake hydraulic line. The switch I used is a small, pendant style switch made by a company called CPI.

The original switches are known as a high wear item, especially with incandescent lamps that draw a lot of current. It's not nearly as bad with LED lamps. The higher current creates arcing on the switch contacts and this requires the lever arm to "throw" further to actuate the brakes and since there's no freeplay adjustment in the linkage it makes it very touchy adjustment.

Momentary Switch | Momentary Contact Switches | Pendant Switches by CPI

CPI is a USA Based designer/manufacturer of waterproof, sealed Momentary Contact Switches (Pendants) used in high performance military and industrial applications.

www.cpi-nj.com

 

[gestut]

Well . Looosened the bolts moved the switch rearward and now slight touch on brake pedal and light come on. But now i noticed leak on my front r hub. Never ends