I have '68 and '70 F-100's and on both trucks the parking brake engaged(fingernail-sized) light doesn't work. I troubleshot the '70 and found a couple of things:

When I re-lamp the fried bulb, it comes on whether the parking brake's on or not (after stripping the meat from my right hand to get at the spring-loaded receptacle behind the dash). Now, I have traced the system and it appears that the light works on a pressure switch mounted to a line block bolted to the frame rail below the master cylinder (dark and scary down there). There's a power plug (which was unhooked) going to the switch (which is screwed in between what I assume is an incoming line and a return). I hooked it back up with no change: light stays on regardless. From my journeys through the junkyards, it would appear this is a common problem with these vehicles: all the fingernail lenses are either bubbled or melted as if the system malfunctioned and the light just kept on burning...

What's up with this? Have I correctly assumed the operation of this system? (God forbid I look for and purchase a shop manual!) What's the fix? New screw-in pressure switch? Who has 'em? LMC doesn't seem to; nor does this site. Ideas? Thanks!

Matt:-X11

 

I was wondering the same thing on mine, but I thought the pressure switch on the brake line didn't have anything to do with the parking brake. I'm not sure of this, but how would a pressure switch on the hydro line know anything about the cable operated parking brakes? Unless it was a two part switch. (just guessing here)

I saw a switch connected to the parking brake on a newer (80 something) truck. It was near where you pull the brake off, mine has a hole there and a stop tab but I haven't seen any older ones with a switch there.

Hopefully someone here knows....

 

I've never heard of an integrated E brake line incorporated into the Brake failure light system.

Maybe someone has a wiring diagram for your year of truck.

let's get to the bottom of this !


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I had a 69 f-250 that had the same problem. I bought it from my grandfather and when asked wwhy he had electrical tape over it he said while pulling a heavy trailer he had slammed on the breaks and the light came on and he couldn't get it to go off so he put tape over it. When I said that it wasn't on he said put a bulb in, I did, It came on, I pulled it and left sleeping dogs lie.

dj

 

To the best of my meager knowledge the light you fellows are talking about is not for the parking brake, it's a brake warning light to let you know if you main brakes are having a problem. It's mounted on the deferential valve, if the brakes become unbalanced due to lose of fluid ect there is a valve in that will move itside (I think it's supposed to save some brakes for emergency stopping in case of failure) The valve trips the light on. There's procedure to reset this switch in the chilton book. Hope this poor explanation helps.
Clint

 

This would explain a great deal! As it is located right above the parking brake release, I have assumed for years that it was intended to tell one when it was engaged. Hmmmm....

Thanks, I'll keep researching.

Matt

 

That’s what it is, a brake warning light. Boy it sure does get hot too! On the later model trucks it’s suppose to center itself by pushing down hard on the brakes (assuming you fixed the problem that caused it to come on in the first place). On the earlier ones, you have to crack open a fitting on the side that didn’t fail in order to recenter the switch. Push a little on the brakes until the light goes off and then tighten the fitting. It’s a pain in the you-know-what sometimes to get it right because it’s easy to go too far.

Barry

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I knew what the light did, but I sure wish I would of known how to reset it when I had the 69.

thanks

dj

 

Matt,
The brake pressure light on my 69 F250 didn't lite when I got the truck, so I removed the bulb to get a replacement,and then reassembled
the socket and light assembly in the dash. The pigtail made contact with the socket while driving and melted the wire to the light asembly
and since that wire is attached to the 12v lead to the ignition switch
it shorted everything out. Word to the wise, disconnect it from the
pressure switch, or insulate the pigtail with electrical tape to keep
this from happening. You may be able to get the red "BRAKE" light
lense from one of the vendors that have reproduction parts for Mustangs or full size Ford products. The same light assembly was used on full sized cars in the mid-sixties, Mustangs I'm not certain though.
I have found a few at the salvage yards with the older cars.

Jan.....

 

The same bezel assy. was used on the Econolines too.

 

Jan,

Not sure how you got your short -- is this inherent to these models == a design flaw? I noticed that mine was unplugged from the pressure switch and reconnected. Should I undo?

Matt

 

Just leave it unplugged. As with all warning lights, it is really a "too late" light. I've had my 67 for 7 years. it has been unhooked the whole time. Mostly becuse the previos moron that owned it used the hot wire for this warning light: TO POWER THE RADIO!
This was amoung many electrical "What the"'s that it had.
Pat