Brake Switch Replacement

[Dasgog]

Hello

So after looking over all of the wiring and what not and seeing nothing wrong I have to assume it is the Brake Switch under the truck that is causing not one but both of my brake lights to stop working at the same time… The rear driving lights work fine as do left and right blinkers.
My question is this, and I believe I have the old style, is that if I take the switch off will there be fluid leaking out and then I need to bleed my brakes again or does it just come off as a whole and replace it and I’m done?

 

[reloader64]

So, it's been awhile since I replaced mine, but I believe fluid will dribble out when you remove the switch. I advise to take a picture of the switch. Compare to pictures on line to see if yours is old style, or new style. Purchase the appropriate switch, replace, and refill the master cylinder.

I got tired of replacing mine every year or so, so I located a weatherproof plunger switch. Welded up a bracket, mounted the switch so the brake pedal arm would activate it, and we're good to go. Hopefully, you'll have better luck with your replacement.

Scott

 

[Dasgog]

So, it's been awhile since I replaced mine, but I believe fluid will dribble out when you remove the switch. I advise to take a picture of the switch. Compare to pictures on line to see if yours is old style, or new style. Purchase the appropriate switch, replace, and refill the master cylinder.

I got tired of replacing mine every year or so, so I located a weatherproof plunger switch. Welded up a bracket, mounted the switch so the brake pedal arm would activate it, and we're good to go. Hopefully, you'll have better luck with your replacement.

Scott

So dribble out a little does not mean I have to bleed the brakes though, or do I? And yes I always monitor the master cylinder. BTW here is a pic

 

[Mullaney]

Hello

So after looking over all of the wiring and what not and seeing nothing wrong I have to assume it is the Brake Switch under the truck that is causing not one but both of my brake lights to stop working at the same time… The rear driving lights work fine as do left and right blinkers.
My question is this, and I believe I have the old style, is that if I take the switch off will there be fluid leaking out and then I need to bleed my brakes again or does it just come off as a whole and replace it and I’m done?

.
I believe you are right reloader64 . An upgraded switch on a friend's truck was having the same problem and he found a "brake pressure switch" that was advertised as weatherproof. We tested by disconnecting the wires off the old switch, taped them together and verified that the brake lights came on. They checked good, then both of us crawled under the truck. He unscrewed and I jammed in the new switch and lost one very tiny drip of something. Can't swear it was brake fluid... Basically a no mess operation and no brake bleeding required.

 

[reloader64]

I never bled mine afterwards. There's no pressure on the system at that point, and the hole the switch screws into is pretty small. You shouldn't lose very much between pulling the old switch out and threading the new one in.

Scott

 

[Dasgog]

Hello

So after looking over all of the wiring and what not and seeing nothing wrong I have to assume it is the Brake Switch under the truck that is causing not one but both of my brake lights to stop working at the same time… The rear driving lights work fine as do left and right blinkers.
My question is this, and I believe I have the old style, is that if I take the switch off will there be fluid leaking out and then I need to bleed my brakes again or does it just come off as a whole and replace it and I’m done?

thank you to you both!!! At a later time I will consider modifying an adapter for it but right now I just need to go drive legally. Thank you again.
I also hope that the switch is indeed my issue… both brakes lights going bad same second is highly suspicious

 

[Mullaney]

thank you to you both!!! At a later time I will consider modifying an adapter for it but right now I just need to go drive legally. Thank you again.
I also hope that the switch is indeed my issue… both brakes lights going bad same second is highly suspicious

.
If I remember, you said the turn signals worked?

If so, the bulb has two filaments. One for "running lights" and the other for "brake lights". You proved the bulbs good. Testing the pressure switch wiring by touching those two wires together (with the lights on) should prove the brake lights. With a new pressure switch, you should be good.

 

[cattlerepairman]

It's not only about a working switch, it's also about eliminating a failure point for the single circuit brake system. The brake switch that is plumbed into the hydraulic part is a bad idea. The switch can fracture and that leads to total brake failure. The military recognized that and upgraded to a brake light switch in the air part of the system, leaving the hydraulic port solidly plugged.
I recommend going that route. While a standard NAPA automotive hydraulic pressure switch is not rated to handle the Deuce's hydraulic pressure, any cheapo air pressure switch will do for this application!

Sent from my SM-G950W using Tapatalk

 

[frank8003]

Don't fix it improper. I used the Haldex switch and even remoted a LED to the dash just to tell me the switch was working. Never failed. Mine did not tell me the rear stop lamps were actually illuminating, just that the air pak switch was functioning properly. It took me 4 hours to find all this so appreciate the effort. I have movies can't be posted here of the installation and many more photos on other drives (somewhre) If interested I can do more and put it on youtube and put links here in SS. I wish to link all my previous posts about this subject again but have failed to find them today, maybe later, wasn't all that long ago. Maybe someone else can find those posts and link them here. I paid $19.99 for the switch delivered, I sure it is MORE now.

BE13250 - Stoplight Switch - Haldex product

Haldex product 'Stoplight Switch' (BE13250): Electro-Pneumatic Switches, Electrical

www.haldex.com

 

[Godspeed131]

I agree with the last two member post about switching over to the air operated switch. Especially if you have to change out the old one anyway. Might as well upgrade to a safer setup . If you can’t source all the parts on your own, Big Mike’s motor pool has a kit already built up. It may be more than you wanted to spend but it’s a one stop shop.

M35A2 BRAKE SWITCH AIR UPGRADE KIT - 12255668

BRAKE SWITCH AIR UPGRADE KIT FOR M35A2. THIS KIT ALLOWS YOU TO SWAP FROM THE ORIGINAL HYDRAULIC SIDE BRAKE SWITCH TO A SWITCH ON THE AIR SIDE OF THE AIR PACK PLUMBING. THE AIR SWITCH IS ALSO AVAILABLE INDIVIDUALLY UNDER # 11602160 PART # 12255668 NSN 2530-01-105-5025, 2530011055025

www.bigmikesmotorpool.com

 

[frank8003]

I agree with the last two member post about switching over to the air operated switch. Especially if you have to change out the old one anyway. Might as well upgrade to a safer setup . If you can’t source all the parts on your own, Big Mike’s motor pool has a kit already built up. It may be more than you wanted to spend but it’s a one stop shop.

M35A2 BRAKE SWITCH AIR UPGRADE KIT - 12255668

BRAKE SWITCH AIR UPGRADE KIT FOR M35A2. THIS KIT ALLOWS YOU TO SWAP FROM THE ORIGINAL HYDRAULIC SIDE BRAKE SWITCH TO A SWITCH ON THE AIR SIDE OF THE AIR PACK PLUMBING. THE AIR SWITCH IS ALSO AVAILABLE INDIVIDUALLY UNDER # 11602160 PART # 12255668 NSN 2530-01-105-5025, 2530011055025

www.bigmikesmotorpool.com

I decided to not like that switch and went with the Haldex.

AIR OPERATED BRAKE SWITCH FOR 5 TON AND CONVERTED 2.5 TONS - 11602160

AIR OPERATED BRAKE SWITCH FOR M939 SERIES 5 TON TRUCKS. THIS SWITCH CAN BE USED AS AN UPGRADE ON OLDER 5 TON AND 2.5 TON TRUCKS TO REPLACE THE FLUID SIDE BRAKE SWITCH. IT IS HOWEVER NOT A DIRECT REPLACEMENT AND WILL REQUIRE SOME MODIFICATION TO WORK. PART # 11602160 NSN 2540-00-789-6192...

www.bigmikesmotorpool.com

 

[Godspeed131]

Oh yea what was the reason? Just curious I haven’t used either. Mine still had the old style fluid switch. I just knew of the kit that big mike had.