Brake warning light/switch

[fonzf100s]

Hey all, I know the light in the lower left corner of the dash (left of ignition switch) is brake warning light, right? I haven't been to the salvage yard in a while but where does that hook up on a drum/drum NO power brake system? Is there a switch that goes somewhere, maybe by the valve in the frame? Or is it just the parking brake light or both? Thanks,


Ron S.

[oldschoolrods]

That is the brake warning light . On a system like you described the switch is mounted on the brake distribution block which is mounted on the drivers side frame rail near the front of the truck. If you have trouble finding it just trace the lines out of the master cylinder.

[fonzf100s]

Thanks, I did find that box in the frame rail, but no switch. Is it a screw in switch like the pressure brake lite switch on '61 to? single master cylynder?

Thanks for the help,
Ron S.

[willowbilly3]

I thought it was just a parking brake warning light. Maybe I was wrong since I never seen one work.

[FORDification]

68F250 described it best when he stated in a thread on the old forums when he said "...everybody said it was a parking brake light but it isn't. It's a brake warning light, if you lose pressure in the front half or rear half of the hydraulic system it comes on. That thing that looks like an "H" on the frame where the lines go is a pressure differential valve. The valve is centered and balanced by the pressures of the front and rear system. If the front or rear lose pressure, the valve goes off-center and trips the brake warning lamp switch that rides on the valve. It also goes off-center when you bleed the system and can be a real pisser to recenter, especially if you're doing it by yourself. A lot of times people just disconnect the plug to the switch, not the best idea."

[willowbilly3]

I have had to fiddle with those a good bit to get them reset. Almost impossible alone. With a helper you can crack the line and just push the pedal very slowly until the light goes out and tighten the line. It might take a couple trys back and forth to get the pedal guy to push just right. I guess I never had to mess with one on this model.

[fonzf100s]

Thanks guys, I'll have to make a trip to the junkyard to find one, because it is nice to have.

[oldschoolrods]

I think there worthless myself, when I lost my back breaks i didn't need the warning light to tell me i was about to be SOL.

[Tim P.]

Hey guys i have a question about the the brass pressure valve where can i get some replacement o-rings for it does it take special kind as i had some problems with mine i dissambled mine and cleaned it and notice that one of the rings were abit worn now it leakes some thru the switch cause of the worn o-rings any thoughts short of shooting it, Thanks Tim.

[fonzf100s]

I've always figured out I've lost brakes when the pedal goes to the floor without a light coming on, just putting everything back original on the truck.

[Tim P.]

look im not concerned about weather the switch is working or not just want to know if there are specific o-rings for this repair as i have found out is that when a o-ring is failing it will leak out around the switch on that h blockif anyone has and input on this specific issue it would be helpful Thanks Tim.

[fonzf100s]

I just got the switch from the junkyard Thursday, but I'm out of town now, is the o-ring on the switch, or in the h block? I'm assuming it's on the switch, so I would just maybe try to find an o-ring at your local hardware/ plumbling section that was the same size, which you may have tried already. Hope that helps a little,

Ron S.

[Tim P.]

The switch doesn't need a o-ring the o-rings are in side the h block on the piston that slides within to equlize the brake pressure i was wondering if it requires special o-rings or will brake fluid deterioate a standard o-ring i know it will take a paint finish off if you get it on paint. Thanks in advance Tim.