This morning when I got to work I noticed what looks like a red lens light of some sort about the size of a nickel right above my emergency brake release handle. It has never been on before, so I have no idea what it is...

I have a 1970 F100 lwb if this helps...

Thanks,
Steven

Got a picture? Perhaps a a trailer brake?

UTfball68 said:

Got a picture? Perhaps a a trailer brake?

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Unfortunately not. Carole has the digital camera and my cell phone takes crappy pictures.

Supposed to be a parking brake warning light the one on my 72 hasnt ever worked.

okay, just curious. Makes sense, though, since it is right beside the parking brake release lever

That is your brake warning light. It is activated by your brake differential valve. The light goes on when there is a difference in pressure between the front and rear brakes. You can find the valve by tracing your brake lines from the Master cylinder to the frame. It's the brass box that your lines go into. In the middle of the valve there is a piston. When there is more pressure on the front or rear brakes, the piston moves from its center position and the brake warning light goes on. This could be caused by a leak in the lines or air in the lines. It is not easy to get it centered.

The way it's supposed to work is, after checking your lines for leaks and after they have been bled, step on the brakes very hard. That's supposed to center the piston. If that doesn't work, since there is no way to tell which way the piston moved so you don't know if it's the rear or front brakes that is the problem, do this: Have someone sit in the cab while you loosen the brake bleeder on one of the rear wheels and have them press on the brakes slowly until the light goes off. If that doesn't work, do the same on the front. If that doesn't work, there is a lot of information on the brake differential valve on www.fordification.com. Do a search for it in the for it on the forum.

Every time the brakes are bled the valve has to be centered. Newer vehicles had springs that helped.

My poston was stuck so I had to take mine apart. It wasn't fun.

Good luck

Oh, the light hasn't come on. I was just curious what the heck it was. Now, though, I know if it comes on I have some work to do.

Thanks for the detailed information.
Steven

1985 Ford F-150, if it doesn't work, it could be a burned out bulb. The bulb can be removed by reaching behind the dash where the light is and turning the housing to the left about 1/4 inch and pulling the housing off. It could also be the switch in the differential valve that activates the light.

Steven, If you need to take the piston out, remove the differential valve from the truck, take the cap off, then heat the housing with a torch and tap it on a block of wood. Heating it will soften the rubber O rings and make it easier to get the piston out. Don't heat it too much because I don't know where you'd get replacements. They are flat, not round. I've also read that people drill a small hole in the end of the piston and put in a screw and use a claw hammer to pull it out.

The other option is to take the bulb out of the warning light and not do anything. I'm glad I got mine to work but I went for years not knowing there was anything wrong until I replaced the bulb and the light went on. Then I was obsessed with fixing it.

Besides searching fordification.com, an Internet search for "brake differential valve" or "brake warning light" will probably help.

71F-100 said:

1985 Ford F-150, if it doesn't work, it could be a burned out bulb. The bulb can be removed by reaching behind the dash where the light is and turning the housing to the left about 1/4 inch and pulling the housing off. It could also be the switch in the differential valve that activates the light.

Steven, If you need to take the piston out, remove the differential valve from the truck, take the cap off, then heat the housing with a torch and tap it on a block of wood. Heating it will soften the rubber O rings and make it easier to get the piston out. Don't heat it too much because I don't know where you'd get replacements. They are flat, not round. I've also read that people drill a small hole in the end of the piston and put in a screw and use a claw hammer to pull it out.

The other option is to take the bulb out of the warning light and not do anything. I'm glad I got mine to work but I went for years not knowing there was anything wrong until I replaced the bulb and the light went on. Then I was obsessed with fixing it.

Besides searching fordification.com, an Internet search for "brake differential valve" or "brake warning light" will probably help.

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Okay, now I'm obsessed with replacing the bulb to see if it comes on. .. Will do that this weekend.

Ill have to swap the bulb out and see what happens. Thanks for the info.

Just a note to those that have BURNT out bulbs ...please save them for me.

I'm looking for about 100 of them.














































































I'm building a dark room.




Really, I can't believe someone is antsy to get light to come on when it is considered bad news when it does

Mil1ion said:

Really, I can't believe someone is antsy to get light to come on when it is considered bad news when it does

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Well since it is a safety thing it might be good to know if it works or not, but that's just me.

73F100Shortbed said:

Well since it is a safety thing it might be good to know if it works or not, but that's just me.

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wareagle said:

Oh, the light hasn't come on. I was just curious what the heck it was. Now, though, I know if it comes on I have some work to do.

Click to expand...

I doubt it's a burned out bulb. And...the light is not supposed to come on...unless the brake fluid is low...cuz that's what the puppy is for.

However, for peace of mind, replace this puppy and the problem (if there is one) is solved.

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

Fits: 1968/79 F100/350 / 1968/79 Bronco / 1968/70 Passenger Cars / 1969/79 Econoline / Note: The switch used in 1967 (on everything-C7AZ-2B264-A)...is 1967 ONLY!

This switch is plastic, threads into the Brake Differential Proportioning Valve, mounted below the master cylinder adjacent to the steering gearbox, or mounted on the left frame rail-inboard of the left front wheel.

This switch has been a notorious POS since day one, cuz it fails more often than women change their minds!

The threads tend to crack allowing brake fluid to seep out. When that occurs, the low brake fluid warning light comes on...and stays on (which you aren't experiencing).

The puppy may also...either burn out, or the wires can come loose from the lil darlin' (which has two tiny male connectors for the plug to attach to).

Thanks Bill for the information and part numbers!!!

Mil1ion said:

Just a note to those that have BURNT out bulbs ...please save them for me. I'm building a dark room and need 100 of them.
Uh huh...If you're building a dark room, why do you need any burnt out bulbs? Just don't turn on the light!

And, if you do want worthless burnt out bulbs, you want us to ship them to Canada, filling out a lengthy customs form in the process, and...

My guess is, you aren't gonna reimburse us for the shipping charges!

Really, I can't believe someone is antsy to get a light to come one, when it is considered bad news when it does.

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The OP became antsy the second he bought the old rolling pile of misery.

And...anytime something occurs he's not familiar with (which is darn near everything...since he has next to no experience with the pile), the antsyness increases!

I used have a photo of that set up

Mil1ion said:

I used have a photo of that set up

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You still do, kiddo...open your peepers and look in the parts catalog.

Shown in Illustration Section 22-hydraulic brake system. I'll let you troll thru the pages to find the correct pic.

Bill, did I tell you I ordered the 1964-72 Ford Truck parts CD from HiPo? Thanks for the recommendation. Now if I can just get lucky and find a maintenance manual at an antique store or yard sale... Heck, I may just go out picking one afternoon on the back roads of NC.

faxonautolit.com (located in Riverside CA) has owners/shop manuals, sales/accessory brochures, salesmans data books and a lotta other things silverfish love to feast on.

Shop Manuals were issued when new models came out, then yearly supplements were added until the model changed again.

So, you will need a 1967 shop manual, and 1968, 1969 and 1970 supplements if you want the factory shop manuals.

Visit some small town Ford Dealers in NC, there's a whole slew of them. I know this...cuz...I've driven over many a NC back road and the entire length of the Blue Ridge Parkway-both ways.

Waltz on in and ask if they have related material gathering dust in a back room.

I'm a long time scrounger, so when I vacation, I always drive back roads, cuz nothing can be discovered driving Interstate Highways where people whiz along at 70 + MPH and the scenery is boring, boring, boring.

You want goodies...drive the back roads. It won't be too long before you develop a 3rd eye too see all sorts of scrummies behind gas stations, barns, in fields and etc etc etc.