How to make the brake warning light turn OFF!

[bwlyon]

As the title suggests, when I recently purchased a 1967 F250 2x4 it had/has a few issues, as it had sit all alone on a cold gravel parking lot of a repair shop/used car dealer for 6 years, with no one to love it ! Well, I purchased it, and decided I would show it some love. One of the 1st issues that had to be dealt with was the brakes the fluid had disappeared in the front master cylinder reservoir, and the brake warning light was on. I filled it up with brake fluid, but of course that didn't fix the brakes completely as the rear brake line broke along the frame rail where mud had collected and it rusted out. Therefore, out came the Honda pressure washer to clean up the frame rails to make it easier to get the old lines out. Fortunately the fittings all came loose with a little effort and a few days of presoaking in panther piss (Penetrating fluid). All the rear brake lines from the distribution block to the wheel cylinders were replaced. I left the lines loose at the new rubber line Y block that mounts to the rear axle housing, and then filled the master cylinder with brake fluid. I then went back to the back brakes and pulled the wheel cylinder bleeder valves out, and cleaned them out so I could bleed the brakes. When I finally got back underneath the truck brake fluid was dripping out of both sides of the Y block on the brake hose (YIPPEE)! I tightened the lines attached to the Y block, and put the driver rear bleeder valve into the wheel cylinder and tightened it. I then went back to the master cylinder, and sure enough brake fluid level was lowering and I topped it off. I went back to the right rear wheel cylinder, and again brake fluid was dripping out of it. I screwed the bleeder valve in and waited a minute or so, and brake fluid was dripping out of bleeder and it was tightened. I went to the driver side, opened the bleeder and waited, and it began to drip fluid I then tightened bleeder valve. I topped off the master cylinder, placed the top on, and then checked if I had good brake pedal feel, and to my amazement the brake pedal feel was great. I was so amazed that the brakes would self bleed, I also did the front brakes after sucking out all the old brake fluid in the rear brake reservoir. All four corners self bleed themselves via gravity, but the brake warning lamp was still on.

Well, after much search and reading I found a post about the distribution block and how it operated the brake warning lamp switch.

http://i48.photobucket.com/albums/f207/ ... tch-on.jpg

On the 67-72 F Series drum/drum and the disc/drum there is a brake fluid distribution block on the inside left frame rail behind the steering gear box. Inside this distribution block is a "slider valve" that turns the brake warning light on via the brake warning lamp switch. If there is a loss of brake pressure to the front or rear brakes,the pressurized side will force the "slider valve" to the non pressurized side of the block and complete the electrical circuit turning on the brake warning lamp. Sometimes even after fixing and bleeding the brakes the brake warning lamp stays on. This is due to the fact that the "slider valve" didn't re-center itself in the distribution block. This is what happened to mine; though I had good brake pedal feel and the pressure was equalized in the distribution block the valve didn't center.

Now to the "Fix"! To re-center the "slider valve" you have to crack open the supply line at the distribution block from the master cylinder reservoir bowl that was NOT the cause of the brake warning lamp coming on, and then press the brake pedal down slowly till the "slider valve" moves to the center thereby opening the circuit and the brake warning lamp should go out. There is a possibility that the pin on the switch itself could stick, but in my case it didn't. On my truck, I was under the truck and my girlfriend in the cab. I cracked the supply line to the front brakes (the back brakes caused the light to come on [was the low pressure side], and the back brakes that are now good are going to force the "slider valve" to re-center when the pressure gets low enough in the front brakes due to cracking open the front brake supply line) at the distribution block, and then the gal turned on the key and pressed the brake pedal and we got nothing. Then I said push harder, as she thought she had hit the end of the brake pedal stroke, and "CLUNK" the 'slider valve went from side of the distribution block to the other and the warning lamp was still on. Well, at least the "slider valve" was free now cause even Lori in the cab heard the Clunk when it moved, so I tightened the front brake supply line. I then cracked open the rear brake supply line at the distribution block and Lori slowly pressed the brake pedal downward and said the magic words, "The brake warning lamp went out"! I then tightened the rear brake supply line then had Lori press the brake pedal a few times to make sure the "slider valve" stayed centered; it did, and the brake warning lamp is now off!

[cep62]

Good job.

[hillcountryflt]

Good write up on the process. Can this be performed as a one-person task?

Would like to resolve the reverse issue on my 69 f100 with manual, drum brakes. Light is not working as the sending unit on the distribution block appears to have broken off. Looks like I will have to disconnect the brake lines at the block, remove the block and then remove the remnants of the old sending unit from the block to install the replacement sending unit. Just not looking forward to disconnecting 40+ year old connections. I have another sending unit that I pulled off of my 71 waiting to be used as well.

[bwlyon]

Good write up on the process. Can this be performed as a one-person task?

Would like to resolve the reverse issue on my 69 f100 with manual, drum brakes. Light is not working as the sending unit on the distribution block appears to have broken off. Looks like I will have to disconnect the brake lines at the block, remove the block and then remove the remnants of the old sending unit from the block to install the replacement sending unit. Just not looking forward to disconnecting 40+ year old connections. I have another sending unit that I pulled off of my 71 waiting to be used as well.

If your brake warning lamp switch is broken, yes, the first task is to dig out the broken switch/sending unit out of the distribution block and replace it with a good switch. Then check to see if the brake warning lamp comes on when you turn on the ignition switch to the run position. If it lights up you will have to center the "slider valve" in the distribution block. If the light does not come on, you will need to crank the engine and observe if the lamp comes on while the engine is cranking (mine comes on while cranking the engine, and goes off when you let the key go back to the run position). If it doesn't you need to check the warning lamp bulb and/or wiring harness. As far as being a one man job to re-center the "slider valve" I suppose it is possible. I just happen to have a willing accomplice to help when I need it. Also, if the lines at the distribution block are crusty and rusty, take a few days and spray penetrating fluid all over the fittings several times before you attempt to loosen the brake lines. I did mine and still almost rounded off one of the fittings.

[hillcountryflt]

Thanks for the info, guess I will start putting the penetrating fluid on the fittings now in anticipation of being able to get the job done in a month or two. My work area is being hogged by the 71, which is sans bed, fuel tank and seat while I work on cab corners and rear wiring.

[Ranchero50]

I had to take mine apart and physically push the pin back to center. Real PITA to do with an engine in the way. I've considered replacing everything with late model parts from a '90's truck just to simplify them. The proportioning valve in the frame rail was a bad idea.

[ultraranger]

'67-'72 F100 through F350 trucks only came with a pressure differential valve --no proportioning valves in the Bumpsides. '67s had a one-wire pressure switch on the pressure differential valve. '68-up models had a two-wire pressure differential switch.

'67-'72 F100s were only available from the factory with 4-wheel drums (power brakes was optional). Beginning in 1968, F250s and F350 were available with factory front discs (power again was optional). The factory front disc F250/F350s used the very same pressure differential valve as the ones used on the trucks with 4-wheel drums. The only difference on the '68-'72 F250/F350 factory disc brake equipped trucks was the addition of a stand-alone metering (hold off) valve that was plumbed inline to the front brake circuit but, no proportioning was used on the rear drum brake circuit of the Bumpsides.

In 1973, ALL F100 through F350 Dentside trucks came standard with factory manual front disc brakes, power was optional. This was also the first year three brake functions were combined into a single brake valve body for the disc/drum brake valves: Metering (hold off) to the front discs, pressure differential sensing between the front and rear brake circuits and for the first time, the trucks had a proportioning feature for the rear drum brake circuit.

[Coolmee1]

That answers my question as to why I have one wire coming out of my valve and my 69 f100 has two wires leading down to it. My uncle Vern the previous owner pass away and I bought the truck from my aunt. So he had the wrong valve.

[ultraranger]

That answers my question as to why I have one wire coming out of my valve and my 69 f100 has two wires leading down to it. My uncle Vern the previous owner pass away and I bought the truck from my aunt. So he had the wrong valve.

Functionality-wise, the '67 pressure differential valve works the same as the pressure differential valve for a '68-'72 Ford truck.

The '67 1-wire pressure differential warning switch sticking out of the valve body will require a 1/2" wrench to remove/install it. The '68-'72 2-wire pressure differential warning switch will require a 9/16" wrench to remove/install it.

Both the 1-wire and 2-wire switches have a 3/8"-24 thread where they screw into the valve body. This means they are interchangeable. If you installed a 2-wire switch in place of the 1-wire switch, you would be able to plug your 2-wire connector to the valve again.

[Coolmee1]

Can I just connect the two wires together on my 69 f100 and use the one wire 67 connector that's in there now. I believe I seen an article about the two wires being in common anyways?

[ultraranger]

Can I just connect the two wires together on my 69 f100 and use the one wire 67 connector that's in there now. I believe I seen an article about the two wires being in common anyways?

You could do that but, it means butchering up your wiring to do this.

Just by simply swapping the switches out, you'll be be able to plug the connector directly into the correct type of switch without chopping up the wiring. The 2-wire switches are available new or, you could rob one from a wrecking yard donor vehicle. --seems like a much better proposition to me than hacking up the wiring.