Hello,
I have a 1990 Bronco. With the vehicle turned off, the brake lights come on as soon as any pressure is applied to the brake pedal. When the vehicle is running, the brake lights do not come on until the pedal is pushed down a good distance. Far enough that when driving the vehicle, the brake lights only come on when you SLAM on the brakes. It seems as though when the truck is running, the pressure necessary to activate the brakes is not enough force on the pedal to activate the brake light switch.

Any help would be greatly appreciated.

Paul Ruffo

 

My '86 began to do this recently - my roomate followed me home the other day and said the lights only came on when I came to a complete stop - stopping firmly. They totally failed to work right after that. I'd recommend first checking the switch on the brake pedal. If you use a test light, you can press the brakes by hand and probe the connector on the back of the switch. There will always be power on one side, and the circuit is completed when the pedal is pressed. The action of the switch should be nearly instantaneous. Another key point to check is the large connector just after the steering column enters the dash. The brake signal wire is carried to the turn signal switch. You should have a one brake signal wire in and two coming out - to split the signal left and right. Since the Bronco uses the brake lights as turn signals, the a malfunction of the turn signal switch can cause problems. You need a wiring diagram to pick out the wires. Probing these wires with the test light while activating the brakes can test the circuit before and after the turn signal switch. I actually found my problem in the switch - strange, but wiggling the turn signal stalk reactivated the brakelights. I had to replace the t/s switch. Let me know if you need more info. I can look up the wires for you, but I'd be very suprised if you don't have a shop manual, like most of us Bronco owners!!

 

Mine does something similar. When i press on the brakes to just slow down or whatever, then they flash like im on and off the brake pedal. When i get closer to stopping and am applying more force then they stay on like they should. Its weird and mine is a 90 as well.