I drive a 1982 F150 and my brake dummy light is on and won't go off, even when my emergency brake is on. I started having some brake problems recently, but didnt figure they were related since there aren't any electrical components to the brakes, so it would be difficult to turn a warning light on... I overhauled all of my brakes to fix the existing brake problem, and the light is still on. Does anyone know why this light comes on, and what might be causing it to stay on? Any help is appreciated, thanks.

 

It is most likely the proportioning valve switch moved off center due to the previous brake problem. Loss of hydraulic pressure on either front or rear will cause the internal valve plunger to move to the failed side and turn on the light. I don't remember the procedure to reset.

 

Ford51, it could be a shorted or broken switch on the prop valve, grounded switch wires, or an un-centered prop valve.

To center the prop valve:
Turn on the ign. sw. to the ON or ACC position.
Make sure the reservoirs are filled.
Push the brake pedal down, and the piston will center itself causing the brake warning light to go off.
Turn the ignition switch to the OFF position.

Now this is in my 81 Ford Truck Shop Manual.

Hope this helps.

 

I had a problem w/ my Brake Light Indicator (rectangular light) beside the turn signals and high beam indicater lights. Mine also remained lit even with the parking brake off. Turns out I needed to tighten up my parking brake cable. There is a little switch on the parking brake assembly, so when it was loose the parking brake pedal would not return up far enough to make the BRAKE indicator light go out.

 

Ditto the answers above, Look under the dash at the e-brake and see it it has a switch on it. Some did and some did not. Most likely and common is the proportioning valve has locked of the front or rear breaks and needs reset. I have never heard of the valve going bad but it could be! Follow the info above and try to reset the valve!

 

I'll check for the E-brake possibilty. How would I tighten it if that's the case?

I dont know that the process listed above for recentering the prop. valve would do anything because u said the light should go off when the brake is depressed. Unfortunately, the light is always on. But any other ideas are appreciated. Thanks for the help.

 

Find the wire going to the proportioning valve switch and pull it off. If the light goes off then the valve/switch is not centered properly or the switch itself is bad. If the light stays on then problem is in that circuits wiring "grounded". I've been told that '80-'83's don't have an emergency (parking) brake switch, only '84 and up. My '83 doesn't have one. I think in some cases you have to "Stomp" the brake pedal really hard to make it center.

 

It depends on the trim level. My 82 F-250 did not have the e-brake light but the F-150 did. It was an XLT trim pkg. Now my F-250 does because the F-150 was a parts truck.

 

That's strange, the factory wiring diagram for '83 doesn't show it, but the factory wiring diagram for '84 does and as best I can tell they show all options that have electrical connections. Reckon yours was a retrofit? Next time I go "junking" I think I'll try to find one to install on my '83. Was it an easy changeover?

 

The 1981 owners manual states as follows:

BRAKE WARNING LIGHT

Regardless of whether your truck has standard or power boosted brakes, it is equipped with a dual master cylinder hydraulic system. If there is a loss of hydraulic pressure in either portion of the brake system, this warning light on the instrument panel glows with the word BRAKE when the brakes are applied. Illumination of the brake warning light indicates a loss of hydraulic pressur in either the front or rear brake system. When properly adjusted, the other brake system is still capable of stopping the vehicle; however, the stopping distance will be increased. Have the brake system checked imediately if the light comes on when you apply the brakes.

CAUTION: The brake warning light should glow momentarily in the START position. If it fails to glow momentarily when you start the engine, have the electrical system checked immediately.

WARNING: If the BRAKE light glows other than momentarily with the ignition lock cylinder in the start position, the braking system should be checked immediately. DO NOT OPERATE YOUR VEHICLE.

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There is no mention of it coming on with the Parking Brake at all. And coupled with the evidence of the owners manual and sales brochure, along with the wiring diagram, there is no option for a warning light on the parking brakes for these trucks, before 1981 at least.

All the evidence that I have states 1984 was the first year, of the Parking brake operated warning light, as standard equipment along with the clutch start cancel switch. This is also backed up by my wiring diagrams, brochures, and my friend at the Ford counter. No paperwork etc even describes such a device before 1984, that I have found.

If someone bought a 1982 or 1983, with a parking brake operated, brake warning light brand new, and has paperwork, (IE: a sales brochure, or Owners guide stating it as an option) I'd be interested in finding that out.


This question comes up more than you'd think.

 

Alright so I guess I'll forget the E-brake possibilties. I tried the method mentioned by turning the battery on, pushing the brake, turning it off, etc. but the light did not go off when I pushed the brake.

Like I said in a previous post, the light is always on. Not just when the brakes are applied or not applied. And as far as I know I havent lost any hydraulic power. I just bled the brakes today since I recently repaired them and right after, had to slam on the brakes to avoid a wreck. As far as I know all 4 brakes locked up because the front end swerved gradually, which leads me to believe the front brakes locked up (but that may be wrong) And I know the rear brakes work since I tested them when I put the drum back on, and they had pressure when I bled them. Also, my brake fluid stays even in the two resevoirs... So I'm not so certain it indicates a loss of pressure. But again that may be wrong.

Where is this valve located? I guess I'll test for an electrical problem first since I dont have any other method to re-center it than the one that I tried. I'll try "stomping" on it this time like listed above. Keep the ideas coming, thanks for the help.

 

Alright stomping on it with the previously used method didn't work either, so the electrical possibilities mentioned could be right. I'll keep trying.

 

I look forward to seeing what you find out because I have the excate same problem. It stays on no matter what but everything seems to work fine. Do you have a brake booster installed...the thing that controles brakes on a trailer?

The owner before me just put some black elctrical tape over the light... so I left it.

 

I have the factory brake booster but nothing to control trailer brakes.

 

Just follow the brake lines from the master cylinder; the differential/proportioning valve is the first thing you come to. Unplug the electrical connector, if the warning light goes "off" its most likely a bad warning switch but it's possible that there is a short in the wire between the warning switch and the ignition switch terminal. If the light remains "on" then there is a short in the wire between the switch and the instrument panel.