brake warning light flickering
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Cross-Country
Joined: Oct 2014
Posts: 76
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From: Canton
brake warning light flickering
Hi Guys,
I've been experiencing an issue with my 1985 F-250 4X4 where the brake light in my instrument cluster sometimes comes on at a hard stop; when it does, pushing down or letting up on the pedal will make it go off, and returning it to the same spot will make it come back on. I've replaced the master cylinder and proportioning valve recently, and have bled the brakes by the book multiple times. The brake feel as good as ever, and i'm getting no air bubbles when i bleed them.
Any ideas? I'm stumped.
-James Huston
I've been experiencing an issue with my 1985 F-250 4X4 where the brake light in my instrument cluster sometimes comes on at a hard stop; when it does, pushing down or letting up on the pedal will make it go off, and returning it to the same spot will make it come back on. I've replaced the master cylinder and proportioning valve recently, and have bled the brakes by the book multiple times. The brake feel as good as ever, and i'm getting no air bubbles when i bleed them.
Any ideas? I'm stumped.
-James Huston
Posting Guru
Joined: Jul 2015
Posts: 2,239
Likes: 5
From: Northeast Ohio USA
Hi Guys,
I've been experiencing an issue with my 1985 F-250 4X4 where the brake light in my instrument cluster sometimes comes on at a hard stop; when it does, pushing down or letting up on the pedal will make it go off, and returning it to the same spot will make it come back on. I've replaced the master cylinder and proportioning valve recently, and have bled the brakes by the book multiple times. The brake feel as good as ever, and i'm getting no air bubbles when i bleed them.
Any ideas? I'm stumped.
-James Huston
I've been experiencing an issue with my 1985 F-250 4X4 where the brake light in my instrument cluster sometimes comes on at a hard stop; when it does, pushing down or letting up on the pedal will make it go off, and returning it to the same spot will make it come back on. I've replaced the master cylinder and proportioning valve recently, and have bled the brakes by the book multiple times. The brake feel as good as ever, and i'm getting no air bubbles when i bleed them.
Any ideas? I'm stumped.
-James Huston
Senior User
Joined: Oct 2015
Posts: 283
Likes: 2
From: Franklinton, NC
Did you bench bleed the master cylinder? You have to make sure all the old fluid is out and the master is bled. Air may be getting in somewhere triping the warning light. Also lift up the parking brake pedal by wire or string ( I had an issue with it had to adjust the parking break hard breaking would trigger the brake light). Someone else may be able to help you test the prop valve.. What I would do would go something like this (going by a test for a 1 wire)
Set a multimeter to continuity.
if its a two wire, ground one prong to a cleared (sanded spot) on the prop valve
touch one lead to the prong on the male connector of the valve
have someone press the breaks.
if it beeps you have air in the line
if it does not move the the next male connector on the valve
have someone press the brakes.
if it beeps you have air in the line
if not look for loose worn wiring the may be rubbing triggiring the light when braking
Set a multimeter to continuity.
if its a two wire, ground one prong to a cleared (sanded spot) on the prop valve
touch one lead to the prong on the male connector of the valve
have someone press the breaks.
if it beeps you have air in the line
if it does not move the the next male connector on the valve
have someone press the brakes.
if it beeps you have air in the line
if not look for loose worn wiring the may be rubbing triggiring the light when braking
Thread Starter
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Cross-Country
Joined: Oct 2014
Posts: 76
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From: Canton
No diesel here, just your everyday 300. I wasn't able to test the proportioning valve because it decided to rain cats and dogs here, but I hope to rule that out tomorrow.
-James Huston
-James Huston
Moderator
Joined: Jan 2001
Posts: 56,980
Likes: 2,735
From: Virginia
Just take the wire off the valve. Also check that wire. If it rubs against metal anywhere and the insulation is rubbed through, the light will come on. All you have to do is ground that wire and the light comes on.
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Thread Starter
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Cross-Country
Joined: Oct 2014
Posts: 76
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From: Canton
I do know now that taking the lead off of the proportioning valve stops the issue; I'll look over the wire in depth tomorrow and report back.
-James Huston
-James Huston
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The Brake Pressure Differential (some people call it a proportioning) Valve Warning Lamp Switch was a troublesome turd from day one.
D5AZ-2B264-A (replaced D0AZ-2B264-A) .. Warning Lamp Switch / Available from Ford & auto parts stores.
1980/89 F100/350 & Bronco / 1980/2001 Econoline / 1990/96 F250/350.
1970/78 misc. FoMoCo Passenger Cars / 1979 LTD II(not an LTD!)/Ranchero/Thunderbird/Cougar/Mark V.
D5AZ-2B264-A (replaced D0AZ-2B264-A) .. Warning Lamp Switch / Available from Ford & auto parts stores.
1980/89 F100/350 & Bronco / 1980/2001 Econoline / 1990/96 F250/350.
1970/78 misc. FoMoCo Passenger Cars / 1979 LTD II(not an LTD!)/Ranchero/Thunderbird/Cougar/Mark V.
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