Brake Light stays on
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Elder User
Joined: Oct 2002
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From: Seattle/Tacoma Washington U.S.A.
Brake Light stays on
umm.... My brake light just came on the other day and it wont go off.
1)What causes this?
2)where is the sensor that makes it turn on?
I know I probably need to bleed my brakes, since the last time I did it the fluid was really old and nasty, so I think I will flush them out one more time and then see if that helps. but if it doesn't why is the light on?
My parking brake used to be way too loose (didn't even stop me from rolling), so I went underneath and took a look and seen how to adjust it (had to soak it for 2 days) but finally got the nut loose and screwed it in a bit so it kept me from rolling, but now it must have got loose again because it doesn't do much anymore...?
Any ideas on why my parking brake does this and why my [size=]brake[/size] light is on?
And what usually causes it to go on?
Worn drums or pads?
Or maybe a fluid sensor?
1)What causes this?
2)where is the sensor that makes it turn on?
I know I probably need to bleed my brakes, since the last time I did it the fluid was really old and nasty, so I think I will flush them out one more time and then see if that helps. but if it doesn't why is the light on?
My parking brake used to be way too loose (didn't even stop me from rolling), so I went underneath and took a look and seen how to adjust it (had to soak it for 2 days) but finally got the nut loose and screwed it in a bit so it kept me from rolling, but now it must have got loose again because it doesn't do much anymore...?
Any ideas on why my parking brake does this and why my [size=]brake[/size] light is on?
And what usually causes it to go on?
Worn drums or pads?
Or maybe a fluid sensor?
Last edited by Racerdave; May 16, 2003 at 01:27 AM.
Posting Legend
Joined: Sep 2001
Posts: 30,255
Likes: 37
Brake Light stays on
Dave-
There is a switch mounted above the brake pedal that activates the brake lights on the back of your vehicle. When the pedal comes up it opens the switch, otherwise it is closed and the brake lights go on.
There is also a brake fault indicator light in the dash that comes on if the proportioning valve shifts due to a brake failure.
There is a switch mounted above the brake pedal that activates the brake lights on the back of your vehicle. When the pedal comes up it opens the switch, otherwise it is closed and the brake lights go on.
There is also a brake fault indicator light in the dash that comes on if the proportioning valve shifts due to a brake failure.
Last edited by Torque1st; May 16, 2003 at 02:57 AM.
Senior User
Joined: Feb 2003
Posts: 339
Likes: 1
Brake Light stays on
Early model's didn't have the master cylinder sensor. The most common reason for the light to come on is an imbalance in the braking system ( I'm assuming you are talking about the "Brake" light in the dash?) You may want to check the rear brake shoe's. They may be severly worn. This can cause both of your problem's.
Postmaster
Joined: Feb 2003
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Brake Light stays on
1. Stop driving the truck! Something is wrong.
2. Check the brake fluid level.
3. Does the pedal go down to the floor while applying the brakes at a stop? Bad Master cylinder.
As stated before the switch is mounted in between the front and back brakes at the proportioning block. If the front or back brakes fail and there is a difference in pressure between the two systems, the switch is forced off center and lights the light. Air in one system (front or back) could cause this. Both times I have seen it a bad master cylinder caused it.
AFTER THE BRAKES ARE REPAIRED, you can reset the switch by pressing down on the brake pedal as hard as you can. It will reset the swithc.
2. Check the brake fluid level.
3. Does the pedal go down to the floor while applying the brakes at a stop? Bad Master cylinder.
As stated before the switch is mounted in between the front and back brakes at the proportioning block. If the front or back brakes fail and there is a difference in pressure between the two systems, the switch is forced off center and lights the light. Air in one system (front or back) could cause this. Both times I have seen it a bad master cylinder caused it.
AFTER THE BRAKES ARE REPAIRED, you can reset the switch by pressing down on the brake pedal as hard as you can. It will reset the swithc.
Cross-Country
Joined: May 2002
Posts: 98
Likes: 1
From: Southeastern Virginia
Brake Light stays on
On my truck, the pedal wasn't returning quite far enough to make the switch (it's under the dash at the top of the pedal arm). I got a rubber tie-down strap and made a pedal return spring so the pedal returns all the way and it solved the problem. There's also some adjustment in the switch (it's treaded so you can move it in or out by rotating it).
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Elder User
Joined: Oct 2002
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From: Seattle/Tacoma Washington U.S.A.
Brake Light stays on
ok it seems to me like everyone thought I was talking about my tail light brake light...... I was talking about the one in my dash not the one in the rear..... I just did some work to the truck and started her up today and the light didnt come on? So I hope it ws just some air in the line, but better safe then sory, takeing it in and hain them looked at on monday.
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Posting Legend
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Brake Light stays on
Well you didn't specify so we had to make guesses. Normally the light in the dash is called the Brake WARNING Light, or the Brake Fault Indicator. 
So we had to address BOTH possibilities.
So we had to address BOTH possibilities.
Last edited by Torque1st; May 18, 2003 at 02:33 AM.
Cross-Country
Joined: May 2002
Posts: 98
Likes: 1
From: Southeastern Virginia
Brake Light stays on
There's a sensor on the proportioning valve (by the steering box) that senses the pressure in the brake system. I think this is the one that also lights the light on the dash. The proportioning valve sets the bias between the front & rear brakes. The light's on for a reason. At first I would assume the light's doing its job and check the brake system. If you've checked the brakes and can't find anything wrong, then it's time to find out why the light is on.
The Chilton's manual for the 73-79 F100 - F150 has very accurate wiring diagrams and is very useful for finding shorts and grounded wires. I used the schematics to find two wires that were pinched together under my truck that were keeping the rear brakes lights on continuously. I'd probably still be looking, but the wire colors in the Chilton's manual were accurate, so once I took the cover off of the bundle going back to the rear of the truck, it was pretty easy.
The Chilton's manual for the 73-79 F100 - F150 has very accurate wiring diagrams and is very useful for finding shorts and grounded wires. I used the schematics to find two wires that were pinched together under my truck that were keeping the rear brakes lights on continuously. I'd probably still be looking, but the wire colors in the Chilton's manual were accurate, so once I took the cover off of the bundle going back to the rear of the truck, it was pretty easy.
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