How does dual switch brake pedal work ?

[HUMMER H1]

hey guys I am wiring my humvee brake lights,
I see there are 3 plugs
One is male with two prongs and two female plugs.

can you explain how this switch works ?
my humvee is 12v electrical , I need a signal to the brake lights when pedal is pressed.

thank you

 

[TOBASH]

Eric. This switch should not be voltage sensitive. The bulbs need to be swapped out, not the switch IMHO.

Just look at the switch in my M1165 and your M1152.

 

[Mogman]

IIRC the two individual wires connect ether way to the brake light circuit, the plug with two wires is for the 4L80 controller
The brake light wires close (short) when the brake pedal is depressed the 4L80 switch open when the brake pedal is depressed.
The brake light switch wires are both marked with the number 75

 

[Mogman]

To work correctly the wires (75) need to be wired to the light switch, there should be matching number 75 harness wires by the switch.
75A and 75B again does not matter which way the brake switch numbers 75 wires are connected.

 

[HUMMER H1]

To work correctly the wires (75) need to be wired to the turn signal switch, there should be matching number 75 harness wires by the switch.
75A and 75B again does not matter which way the brake switch numbers 75 wires are connected.

thank you sir,
On mine the numbers say 810 A and 810b,
So basically the two female wires complete the circuit when Brake pedal is pressed correct ?

 

[Mogman]

Yes but an ohm meter will confirm, according to the standard wire list wire number 810 is part of a traverse/elevation system so I am confused at why you are seeing that number.

 

[frauhansen]

One is the switch for the brake light and the other is the switch that tells the transmission controller that the brake is applied.
Synchronizing both is a nightmare cause of short pedal travel of the HMMWV!
I have therefore switched the Siganl for the transmission control unit via a relay. I pick up the brake light directly at the bottom of the switch and operate the Reais. Result = 100% synchronous, always!

What I can not believe so reht is that your HMMWV is a 12V vehicle. Who on earth converts a HMMWV to 12V? And why?

 

[TOBASH]

Eric will not be needing the tranny controller as he is installing a separate controller because his harness was pretty cut up.

He converts his hmmwv’s to 12 V a lot. Given he has 300,000 miles on one of them that he built from parts in boxes, I believe he gets it done correctly.

T

 

[HUMMER H1]

One is the switch for the brake light and the other is the switch that tells the transmission controller that the brake is applied.
Synchronizing both is a nightmare cause of short pedal travel of the HMMWV!
I have therefore switched the Siganl for the transmission control unit via a relay. I pick up the brake light directly at the bottom of the switch and operate the Reais. Result = 100% synchronous, always!

What I can not believe so reht is that your HMMWV is a 12V vehicle. Who on earth converts a HMMWV to 12V? And why?

when I bought this vehicle it was supposed to be parts truck, most wiring was cut and parts missing.
No starter
No generator
No control box
no PSB box
Broken lights
No gauges

so I thought to myself, I had 12v shut of solenoid laying around, I said let me try to start the engine and see if it runs, if it does I won’t part it out,
Sure enough it started rights up.

at that point I had to choose to stick to 24v and source all the parts, or swap to 12v and use parts that I already had.

believe me I wish it was 24v original wiring is extremely well built.
but now it’s all done and everything is
All properly wired and vehicle is drivable,

I am using stand alone transmission controller
12 v glow plugs
Manual glow plug heater with ford starter solenoid
8 groove pulley on a Ac DELCO alternator.
it’s actually very simple reliable setup.

 

[HUMMER H1]

To work correctly the wires (75) need to be wired to the light switch, there should be matching number 75 harness wires by the switch.
75A and 75B again does not matter which way the brake switch numbers 75 wires are connected.

you are absolutely right, the number is 75a and 75b
On the brake light switch female connectors

I was looking at the male plug, that says 810a and 810b

 

[TOBASH]

One thing about Eric…. He just gets it done. He makes it all work and has no time for excuses.

 

[HUMMER H1]

One thing about Eric…. He just gets it done. He makes it all work and has no time for excuses.

haha
I have to go get lost in the middle of nowhere,
No time to waist

 

[Mastherr]

Hi guys, any clue why after removing all 3 wires from the brake switch (75A, 75B) the break warning light remains ON all the time?????

Also, don't know if it has anything do with it... but my M1151A1 is running only on 1st and 2nd gears... doesn't engage 3rd and 4th.... could this break switch sensor screwing up the gear box?

 

[Mogman]

Hi guys, any clue why after removing all 3 wires from the brake switch (75A, 75B) the break warning light remains ON all the time?????

Also, don't know if it has anything do with it... but my M1151A1 is running only on 1st and 2nd gears... doesn't engage 3rd and 4th.... could this break switch sensor screwing up the gear box?

Wires #75 are for the brake lights, they have nothing to do with the brake warning lamp
Unplug the wire from the brake equalizer and see if the light goes out.
The brake warning light is only connected to the parking brake switch and the brake equalizer.
The equalizer is the aluminum block next to the master cylinder that the brake lines run through after leaving the master cylinder

 

[Mogman]

Hi guys, any clue why after removing all 3 wires from the brake switch (75A, 75B) the break warning light remains ON all the time?????

Also, don't know if it has anything do with it... but my M1151A1 is running only on 1st and 2nd gears... doesn't engage 3rd and 4th.... could this break switch sensor screwing up the gear box?

You need to read the codes on the transmission TCM to start with to troubleshoot the transmission.

 

[Mastherr]

Tks Morgan, I’ll check the break equalizer and let you know.
There are no codes on the transmission, when jump wiring, all clear.

is there any other method (electronically) to find out if the system is in limp mode?

 

[Mogman]

Tks Morgan, I’ll check the break equalizer and let you know.
There are no codes on the transmission, when jump wiring, all clear.

is there any other method (electronically) to find out if the system is in limp mode?

I would be surprised if it only shifts into 2nd and there are no codes, other than the continuous code 12, did you disconnect the batteries before retrieving the codes?

 

[Mastherr]

I would be surprised if it only shifts into 2nd and there are no codes, other than the continuous code 12, did you disconnect the batteries before retrieving the codes?

Dear Mogman, first I really appreciate your help. I have just disconnected both batteries entirely. Went to the TCU - jump-wired (A) and (E). Reconnected the batteries. Flipped the ignition switch to check the transmission codes.....

Again nothing. I'll attach a video, unless I'm missinterpreting it.....

 

[Mastherr]

.

 

[Mastherr]

Dear Mogman, first I really appreciate your help. I have just disconnected both batteries entirely. Went to the TCU - jump-wired (A) and (E). Reconnected the batteries. Flipped the ignition switch to check the transmission codes.....

Again nothing. I'll attach a video, unless I'm missinterpreting it.....

The way I see it, the vehicle is on "limp mode"! No transmission codes!... The only other visible clue is the break warning light (Red) always on.... Could this be the troubleshooting route to follow?