Two Electric Switches on Brake? (BOO) -

V6 (1994-2004) Mustangs Technical discussions on the 3.8L and 3.9L V6 torque monsters

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Old 07-10-2013, 05:01 PM   #1
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Join Date: Jul 2013
Location: Nevada
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Default Two Electric Switches on Brake? (BOO)

I'm helping youngest step son with some brake light issues, 2001 Model Year V6 Mustang. Topic = Brake On / Off switch, also known as the BOO switch.

As I understand it, an electric brake light switch does three things:
--Tells the cruise control to shut off when pedal is pressed.
--Turns on the brake lights when pedal is pressed. (duh!)
--Disengages the Transmission Park interlock, such that you can only shift from park to drive when the brake pedal is pressed.

That stuff totally makes sense.

What I'm very confused about is there are two (count 'em TWO) electric switches on the 2001 Mustang. There is a large plastic blue/white switch located up high on the brake pedal, and a smaller black switch located lower just above the drivers foot. The blue/white plastic switch has a large molded in place plastic split pin that mounts into a round hole, and the lower part of the switch is a white plastic cylinder with a C shaped molded end that snaps onto a yellow plastic pin. Blue/White switch wires are green / brown at a short pigtail and they switch at an inline hardshell connector to green/r and orange/XXX. (I only have one photo, car is not here..) The black switch mounts to a welded rod, retained with a yellow spring type cotter pin. Black switch wires = LG/R and R/LG

I'm pretty sure the blue/white switch controls the brake lights and shift interlock, and I presume the other switch is for cruise control shut off. The push rod on the blue/white switch has a little bit of adjustment built into it.

I've worked on this before, but now stepson has the car out of state, experiencing new issues with brake lights and interlock.

I'm assuming there are two switches there because of a late content addition to the model year, probably the shift interlock. (Been there, done that.. I worked for Uncle Henry in Dearborn for 29 years in engineering, new model launch, etc...)

Anybody know the wiring diagram for these two switches? If I was still in Michigan I'd hop right over to the Ford Research Center library and look up the Electrical and Vacuum Troubleshooting Manual (EVTM) for this model, but alas I'm now living in Vegas.

Is there any ties between the two switches? Are these two independent switches wired totally separately or is there some sort of tie in between the two?

I've got a Haynes manual, but for this, the schematics are not all that great. They show two different switches on different pages, with EXACTLY the same colors, so I can't tell much from there.

I fixed this a month ago, by simply reseting the self adjust feature on the blue white switch. The car was pretty low on brake fluid, pedal had pretty long travel. Refilled the brake fluid, reset the blue/white switch self adjust travel feature short. Not sure what's going on now. Stepson swears the black switch is inop. I doubt it but I'm not really sure... He's just learning basic electricity and how to use the volt ohm meter.

Car now has no brake lights, no shift interlock control.

Anybody been here, done this before?

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boo switch, brake lights, interlock

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