Ford Truck Enthusiasts Forums - Brake light keeps coming on, pedal drops a bit

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- 1973 - 1979 F-100 & Larger F-Series Trucks (https://www.ford-trucks.com/forums/forum38/)

- - Brake light keeps coming on, pedal drops a bit (https://www.ford-trucks.com/forums/1570992-brake-light-keeps-coming-on-pedal-drops-a-bit.html)

El Caballo

02-01-2019 08:08 AM

Brake light keeps coming on, pedal drops a bit

Well, my brake lights keep coming on and my brake pedal has some play up and down. I’m guessing that my master cylinder is starting to go. But isn’t there some return spring up there at the pedal pivot point?
I have only had it for about a month now and I’m still getting used to having manual brakes after about a twenty year hiatus from them. Still plenty of pedal feedback, but I’m taking this as a warning sign.

67xr7kat

02-02-2019 12:38 PM

Re: Brake lights ...

Lubricate the pedal pivot under the dash and check the nylon end bushings for wear

Blue and White

02-02-2019 01:43 PM

The brake light switch should be adjustable. Usually you pull the wire and screw it in or out to get it right then re-install the wire.

NumberDummy

02-02-2019 04:21 PM

If the brake light that keeps coming on...is on the dash, it's controlled by this: The Brake Pressure Differential Valve Warning Lamp Switch that threads into the Brake Pressure Differential Valve.

When the brake fluid in the master cylinders reservoir is low, this light comes on and stays on.

The switch is the same 1968/79 (C8AZ-2B264-A), but what year/series is the truck?

El Caballo

02-03-2019 07:44 AM

Quote:

Originally Posted by NumberDummy (Post 18457101)

I should clarify, it is the tail light brake lights that keep coming on. I have a 1978 F100 2wd 302

NumberDummy

02-03-2019 11:59 AM

Quote:

Originally Posted by El Caballo (Post 18457999)

I should clarify, it is the tail light brake lights that keep coming on. I have a 1978 F100 2wd 302

Brake (stop) lamp switch threads into an adapter that clips onto the brake pedal.

If the brake lights keep coming on, the switch is out of adjustment, or one or more of the prongs that retains the adapter to the pedal broke, a common occurrence.

"Newer" replacement switch uses nuts to retain it to the pedal, eliminating the pesky adapter.

El Caballo

02-03-2019 04:24 PM

Quote:

"Newer" replacement switch uses nuts to retain it to the pedal, eliminating the pesky adapter.

The one in there was held in with a zip tie. :-/

Thank you Number Dummy.

RustyTank

03-06-2019 02:19 PM

Quote:

Originally Posted by El Caballo (Post 18454331)

Well, my brake lights keep coming on and my brake pedal has some play up and down.

Same sort of thing was happening to me recently. I picked up up a new brake light switch, looks to be the same kind as the old one but the new switch has the nuts as NumberDummy mentioned. Fixed the problem, brakes actually turn off now when I let my foot off the brake.

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