Brake light
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Laughing Gas
Joined: Oct 2009
Posts: 873
Likes: 56
From: Merlin, OR
Brake light
As long as I've owned my truck, the brake light has been on. Well the last time I drove it, the light has been off, and coming on periodically, then going off again. What do you think the problem could be? Prop valve? Brake pressure warning switch? Or both? Any ideas would be appreciated.
Moderator & parts slinger
Joined: Feb 2007
Posts: 50,124
Likes: 5,773
From: S/W Missouri, Polk county
Normally that light is suppose to come on when you have a serious brake problem. Like a sudden loss of fluid from the system some where. Blown rear wheel cylinder, rusted frame line, ruptured rubber line going to rear axle?
And to prevent that, the proportional valve piston moves to stop the rapid flow of fluid and trip the light.
Since its been on most of the time, have you brakes been normal? Sounds like the truck had a brake fluid loss issue sometime and was fixed and the PO could not get the pro valve piston to recenter.
Sounds like it has fixed itself, I would suggest a full brake system bleed.
And to prevent that, the proportional valve piston moves to stop the rapid flow of fluid and trip the light.
Since its been on most of the time, have you brakes been normal? Sounds like the truck had a brake fluid loss issue sometime and was fixed and the PO could not get the pro valve piston to recenter.
Sounds like it has fixed itself, I would suggest a full brake system bleed.
Ford Parts Specialist
Joined: Nov 2006
Posts: 88,826
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From: Simi Valley, CA
The plastic low brake fluid warning light switch threads into proportioning valve. It's notorious for developing cracks in its threads, causing brake fluid to seep out.
When this occurres, the low brake fluid warning light on the dash comes on...and stays on.
C8AZ-2B264-A .. Low Brake Fluid Warning Light Switch / Available from Ford and a gazillion autoparts stores.
Applications: 1968/79 F100/350, Bronco and Econoline, 1968/69 FoMoCo Passenger Cars (1967 is one year only).
When this occurres, the low brake fluid warning light on the dash comes on...and stays on.
C8AZ-2B264-A .. Low Brake Fluid Warning Light Switch / Available from Ford and a gazillion autoparts stores.
Applications: 1968/79 F100/350, Bronco and Econoline, 1968/69 FoMoCo Passenger Cars (1967 is one year only).
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1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks
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