Do I need to bypass the brake switch

I installed a 98 booster and master in my 89 xj. it is a trail only vehicle so brake lights are not crytical. I have a white plunger switch way up the pedal bar and a four wire switch at the booster bar/pedal bolt.

I can not put this four wire back in and one wire is missing anyway. do I need to worry about finding the missing connection and putting a switch on any of these wires or are they just related to street functions?

That's your brake light switch. I think you need brake lights on the trail if you wheel with other people though. There should be a white wire, that's the power to your brake lights. You just need a power source to the switch & you'll have brake lights. I'd use a GM two wire brake light switch just to simplify things.

I do plan on making the brake lights work eventually but I am using the jeep on the 6th at RC and just wanted to make sure that I was not going to burn something up in the trans if the existing switch had someting to do with something operational.

I just have to hope that whoever is following me is smart enough to keep there distance. most buggies dont have brake lights so I should be ok untill I have some time.

cherokee chuck said:

That's your brake light switch.

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No that is not the brake light switch on an 89. An 89 has the brake light switch is much lower on the pedal. That white switch makes contact until you hit the pedal so you'd have to use a relay to reverse that if you wanted to use that switch for the brake lights.

I do agree that you should get the brake lights working.


From my response to you in the other thread:

That white switch tells the trans computer to unlock the t/c when you hit the brakes. If its not working then the trans computer thinks you have the brakes on and never locks the t/c up which results in higher heat in the tranny and poor mileage. I doubt you'd notice much of a difference off-road either way. In fact the biggest complaint about an automatic off-road is that it doesn't lock the t/c going down hills which means no engine braking.

The other function of the switch is to tell the cruise control when you hit the brakes. The switch also releases the vacuum on the cruise solenoid just to make sure it lets goes when its supposed to. That's to avoid the Audi 5000 type sudden acceleration type incidents (although Ralph Nader put it best when he said the dumb shits had their foot on the gas instead of the brake).

That switch doesn't control the brakes lights. Thats the switch lower down on the pedal.