So I have one brake light just above the parking brake release lever, on the lower left of the dash. I'm not sure if this is the brake malfunction light or the parking brake indicator. I put a new bulb in it since I originally thought it was a parking brake warning lamp that wasn't working. The bulb in there was cracked, so I replaced it. Now, it's constantly on when the truck is on.

After a forum search I found that this might be either a brake system warning lamp or a parking brake lamp. It has the word "Brake" on the red plastic lens. Can someone help me figure out what might be the problem? Where is the actual switch? I want to test it. Perhaps unplug the switch to see if it is indeed controlling this lamp, etc.

thanks.

 

A parking brake warning lamp was a pretty rare feature, but since yours looks to be a Ranger then it might have that. Look at the parking brake mechanism, the switch should be pretty easy to see if it has one. Typically, though, that is just a brake malfunction indicator.

 

OK, I'll have a look. At first glance I didn't see anything resembling a switch, but then again, I'm not sure what I'm looking for. I was just looking for a wire or something.

 

^ ^ So what else is new? This has been a very common problem since day one.

The Parking Brake Signal Lamp was a dealer installed accessory, its switch mounts on the park brake control. Less than 1% of these trucks had one.

But...every 1967/72 has a low brake fluid warning light and the POS switch that controls it.

C8AZ-2B264-A .. Low Brake Fluid Warning Light Switch / Available from Ford & autoparts stores.

Applications: 1968/79 F100/350 & Bronco / 1969/79 Econoline / 1968/69 FoMoCo Passenger Cars (1967 "all" is one year only: C7AZ-2B264-A).

This POS switch is plastic, threads into the Brake Differential Proportioning Valve. It's notorious for developing cracks in its threads...causing brake fluid to seep out.

When this occurres, the low brake fluid warning light on the dash comes on...and stays on!

 

Thanks, Bill. Where is the Brake Differential Proportioning Valve? Is it attached to the master cylinder?

 

It's below the master cylinder, adjacent to the steering gearbox...on some.

Mounted on the left outer frame rail inside of, or just to the rear of the left front wheel...on others.

The switch has two male connectors (pins).

 

You can just unplug it Proportioning Valve it's in the middle of it. Plus if a wheels cylinder leaks it will trip the Proportioning Valve inner control rod moves and grounds the tip of the screwed in switch causing the light to come on. The rod is o-ringed on each end. The center is smaller so the tip of the switch does not touch until is moves off center. So when there's no fluid at one end of the Proportioning Valve the inner rod shifts to that side with the leak or with no fluid. I found with yrs of crap floating through the system and settles in the Proportioning Valve freezing up the rod.If the Rod has not been reset after the system has leaked enough fluid to cause the inner ROD to move and ground the switch. I've managed to rig up some tube nut plugs on one side of it and also on the master cylinder to. Having one master cyl. line hooked up it took 2 feet pushing on the brake peddle and a rag over the Proportioning Valve to catch the inner rod when it comes out. Wow it was stuck good. I used brake cleaner and a brass brush to clean the inner rod. I cleaned the Proportioning Valve once removed with a gun bore brush, the longer you can soak it in some cleaner the better.Do this or buy a new one for well over $75+ bucks. Once installed self bleed from master with the lines loose at the bottom, once fluid dips out tightenthe hard lines on both ends where they Tee off to front & rear wheels. Oh Ps when reinstalling wet the inner rod with B-fluid. Make sure it's center in the Proportioning Valve. If you damaged the o-rings your your pretty well screwed at it not leaking. If any brake fluid comes out from the plastic trip switch the o-rings our bad or it's crap inside may have damaged the o'rings. Well hope you can fallow this as it's passed my bed time and took my pain meds already..
orich

 

THanks Bill and Orich. Orich, I'll follow your instructions carefully.

 

Oh one thing never remove the light bulb and leave the socket empty.
Like many have done and me. Or you maybe sorry. This has caused many guys to have to replace the under dash wiring loom. Or if you can remove the Batt. cable fast enough while it cooking, you can repair it. I had removed mind bulb back in 1978 after getting the truck. I put in a new bulb and after trying to reset the push rod in the P-valve after doing a brakes job. I gave up and after a week of driving with that damn red light on, (I removed the bulb) and 20 yrs later it worked forward and shorted. Found out it was not fused and just heated up red hot melting all the insulation that came in contact with in the loom..I was lucky enough that it only cooked about 3.ft that needed repairing.. Yup it came back to haunt got me. So leave an old burned out bulb in the socket until you fix your P-valve.. PS I've since put a fuse in-line and added a E-brake light switch setup. So now the light comes on when E-brake is set. I fixed up a switch on the cable itself. Spliced into one wire from the p-valve switch. As it's just one wire to ground ez fix..
orich

 

Ah, wow. Thanks for that important detail!

Last night, I tried to find the switch that controls it, thinking I could just detach one leg of the wires for now. But, I think the master cylinder and proportioning valve were changed at one point since they are made by CPP. There's a plug on top of the P. valve which has 1 wire coming off of it. It is not connected to anything and merely wraps around a old looking plug coming from the cab. That plug has a short wire shorting one terminal to the other. I removed it, thinking this must be the original plug that connected to the OEM P. valve, but it didn't cause the light to turn off. I just can't find were the wires from the light go. They go into a wire loom under the dash and get lost in all the wrapping. The colors of the wires are Purple and Red/Yellow-stripe.

 

Hmm that's the switch and plug with the wires are Purple and Red/Yellow on it. The light should go out when unplugged, Make sure the plug end don't touch any metal and ground it. Check to see if there is any voltage at the plug term. With a test light or voltmeter. One lead to ground and one lead in the plug term. socket
orich

 

I have to find that right plug first. I don't see a purple and red/yellow wire in the engine bay. Still looking for that. When I get home, I'll continue my quest. I do have a tester.

Thanks, Orich!

 

Really? Jesus, I've had my bulb out since 2002! Maybe I will have to look into that this weekend then.

 

this might help

http://www.fordification.com/tech/wi...-70_master.jpg
and here is one that gives you the colors
http://www.fordification.com/tech/wiring/68-23.jpg
pay close attention to wire #640 (red/yellow stripe) that goes to your IGN
and #977a which is Violet and goes to your DUAL BRAKE WARNING SWITCH

 

Wow, bumpside. thanks a lot for that diagram! That's very helpful. I've been studying it for a while now. What I don't get is that on the first chart it shows #640a and 932 combining into one connector that connects to the Carb Throttle Solenoid. What/Why is that? Is that solenoid acting as the ground leg of the circuit? The brake warning switch merely connects/disconnects the hot side of the circuit?