My new 1967 F100 has a few things I'm working through. One item is the handbrake red light stays on even when I pull the release for the handbrake. I'm wondering whether its just the switch that's not cutting the circuit to the red lamp bulb or if my rear brakes might be binding... the truck seems to drive fine though so hence the thought on the switch. Any ideas on where the switch is to check it? Thanks

 

I dunno even if it has a "parking brake warning lite"... the lite on later models is to indicate whether either of the brake circuits failed.

For the latter, the switch is on the brake distribution block... but 67s tend to be a strange animal.

Others will chime on shortly....

 

This light has nothing to do with the parking brake! Some people assume this, because it's located above it on/under the dash.

C7AZ-2B264-A .. Brake Pressure Differential Valve Warning Lamp Switch / Obsolete

This plastic switch threads into the Brake Pressure Differential Valve located below the master cylinder. It's notorious for failing!

Applications: All 1967 FoMoCo vehicles ONLY. The switch used 1968/79 is different.

MUSTANG'S ETC. in Van Nuys CA has 1 = 818-787-7634.

KLIMESH MOTOR SALES in Calmar IA has 1 = 563-562-3241.

PEROGIE ENTERPRISES in Highstown NJ has 1 = 609-448-5593.

MUSTANG SERVICE CENTER in North Hollywood CA has 1 = 818-765-9266.

 

Bob's your uncle.

 

Ford brake systems first went to tandem MCs in 1967 (so did all other domestic vehicle manufacturers --under a federal mandate to discontinue use of single reservoir MCs after 1966).

'67 was the first and only year Fords had the single pin brake pressure differential warning switches.

Beginning in 1968, the pressure differential warning switch went to a two-wire switch, although the two pins are linked together at the lower ends of the pins.

The second wire from the switch goes back to the start circuit of the vehicle. When you turn the key to the 'start' position ('68-up), the red brake warning light will momentarily flash on, until the key is moved to the 'run' position of the key switch, at which point the warning light goes out. This is a prove out circuit to let you know the bulb and that the brake system is good.

A '67 wont have a prove out circuit but, if the red warning light stays on, it's telling you there is (or has been) an imbalance of pressure between the primary (front) and secondary (rear) brake circuits.

If you haven't serviced/replace any hydraulic brake components on the truck lately, it means there's a legitimate problem going on with the brake system.

 

Hey, at least yours works.

Ive lost all brake fluid in the rear brakes numerous times
and have never seen the thing flash once.

 

I didn't know what I was going to do with the brake light since I don't have the stock proportioning valve any more. Now I do, a parking brake warning light. It shouldn't be too hard to rig up a switch to the parking brake.

 

1967 F100 Master


Took a picture of my master cylinder and couldn't see this plastic switch. (attached)


Is it supposed to be on the master cylinder itself or might I have a newer one and the light might be something different...? The vehicle is new to me and I'm used to my modern German Brembo car brakes and these in comparison feel very spongy....anything else I should check?

 

Yours is looking pretty identical to mine.

My light has the wiring, but nothing on the MC that yours doesn't have.

My light also doesn't work though.

I took a video using my phone and I will upload it and show you.

Luckily I have the gauge cluster out so you can see the wiring in the video.

 

Here, I messed up the angle of the camera.
I'll know better next time

Quality isn't the best, but you can see it.

On a 1967 F100 4x4.


Shows the MC / brake lines coming from MC.
Tried to get both sides.

Showed that little red light and the back wires.
Never seen the light go on even though I know it should have been.

Not too sure what is missing.

Anyone with a properly working one have any photos / video?

 

The plastic pressure differential brake switch is located in the pressure differential brake valve.

The brake pressure differential valve is located on the inboard side of the left frame rail, directly behind the steering gear box.

It will look like this.



The inner workings of the valve looks like this (upper half of photo).



As long as the pressure differential 'piston' is centered in the valve body, the warning light will remain off --as it should be if the brake system is functioning properly.

If there's a differential in system pressure, --a rear wheel cylinder blows out for example, the secondary (rear) brake circuit will have a lower pressure compared the the pressure on the primary (front) brake circuit.

The higher pressure of the good side will force the piston of the valve over to the lower (failed) side. This will close the contacts inside the plastic switch. This will complete an electrical path to ground, through the body of the valve assembly, and illuminate the red warning light on the dash.

The pressure differential valve does not have to be powered up through the vehicle's electrical system to determine if the valve is shifted or if it's centered. --shifted = Bad. Centered = Good.

As I mentioned earlier, '67 model Fords will only have one contact pin sticking up inside the switch, where the wiring connector pigtail plugs into the switch. '68-later switches will have two pins but, the two pins are linked together. On a '68-later switch, it doesn't matter which contact pin you put a meter lead to. --They're at the same electrical potential.

'68-later pressure differential switch. (you can see the bar linking the two pins together).



Place one meter lead on the pin (doesn't matter which one) and one meter lead to the body of the valve. If the piston (valve spool) inside is centered, a multimeter will read infinite resistance (OL --Open Line). If the multimeter has an audible feature (my Fluke does), there will be no 'beep.'



If the valve spool is shifted, the meter will show a resistance value. If the meter has an audible feature, the meter will beep.