I have a 91 F150 lariat 4x4. my problem is that the cruise control will not disengage when i press the brake. this problem almost caused me to have an accident.

A car in front of me rear ended someone on the freeway going 70. when they slammed on their brakes i had to slam on mine, all the truck did was slow down then downshift and launched me back up as if i had no brakes, luckly there was no cars on the left lane that i was able to swerve out of the way before it was too late.

ive tested this at slower speeds and it does the same. does not want to disengage the cruise control. anybody have any idea what i can check to fix this?

 

I'm not gonna be much help, but there would have to be a switch on the brake pedal that signals the cruise control to turn off (or at least it seems that there should be).

There is a brake light switch that turns on your brake lights when you push the pedal - does it work? Maybe there is another switch down there if it doesn't run off the same one.

 

The pressure switch for these are mounted on the frame rail on the driverside almost directly below the master cylinder. There is a recall about the switches leaking internally and causing fires. I would have it checked out before using the cruise control again.

 

So it's mounted on the frame rail in line with the brake line? And senses pressure in the brake lines instead of simple pedal action?

Interesting... I'm only asking because I never had thought about it before, so this is good info to learn about.

 

You are thinking of the newer models. This truck should have a vacuum switch near the pedal that should be checked for adjustment or vacuum leaks.

Of course, I could be wrong. My truck doesn't have cruise control.

 

The vacuum module is used to control throttle and maintain speed the brake sensor sends signal to turn off the cruise control. My 93 has a electronic speed controller I am not sure when they switched from the vacuum to the electronic control measures I think that it is the same time they switched to electronic speedometers.

 

Sounds good to me. Electric speedometers started in '92 so the cruise control system must have changed then too.

 

ok, so i think ive figured out why my cruise control isnt coming on. whenever i press the brakes, the brake lights dont come on. but my parking lights and turn signals work. anybody know what switch or relay i need to replace to get them working again?

 

Looks like Aliens hit the jack pot, your brakes switch should be under the dash on the pedal linkage. On my 02 the cruise control recall switch is screwed into the master cylinder. Wonder if my switch on the master does both functions. Have to look at that. Good luck.

 

Get down under there and look around. On the brake pedal lever under the dash, there should be two switches (at least there are two on my 91). I'm guessing that one is the brake light switch and one is for the cruise control - I haven't traced the lines to see what goes where, but if you can get yourself twisted up under there to see them, you should be able to do just about anything!