brake light on, pads good

vdubstreets · 12-04-2009, 03:50 PM

I picked up this 99' Cherokee sport 4.0 auto for a winter beater and I'm fixing it up slowly. So one issue i just saw that I'm working on is the brake light is on. I check the front pads and they look like they were just changed. I also checked the fluid in the reservoir and that is also good.
What else could cause the brake light to be on? any sensors?

ehall · 12-04-2009, 03:54 PM

two things will turn it on, first is the parking brake switch, the other is a hydraulic switch in the proportioning valve

disconnect the wire from the switch on the valve, if the light goes out then you have a hydraulic problem. if it doesn't go out, the parking brake switch is on

vdubstreets · 12-04-2009, 03:55 PM

Thanks for such a fast response, I'll check it out tomorrow if its not snowing.

vdubstreets · 12-13-2009, 12:31 PM

Had to fix a couple other things, but while i was under the hood i took off the plug that is proportion valve and the light went off. So I'm going to go ahead and assume its a "hydraulic problem".

The peddle feels fine, but i read around it could be uneven pressure so I guess a start would be to bleed the brakes. but i also should check the rear shoes.

skyway0018746 · 12-13-2009, 01:59 PM

could be that the switch is bad , ive only had mine come on when there is air in the system so bleed them and see what happens. or you jack the back up and put it in gear and see how it stops

AZ Jeff · 12-13-2009, 07:14 PM

Quote:

Originally Posted by skyway0018746

could be that the switch is bad , ive only had mine come on when there is air in the system so bleed them and see what happens. or you jack the back up and put it in gear and see how it stops

Here is the issue that will cause the light to go on: while servicing one side of the brakes, a bleeder screw is opened and the one side is bled while the other side is closed. Depending on how much pressure differential exists when one side is opened, the "spool valve" that controls the pressure switch inside the proportioning valve assembly moves to one side, tripping the pressure switch.

THE FIX: Have an assistant sit in the vehicle with the key "ON" so the brake light is illuminated. Open a bleeder on the OPPOSITE part of the brake system while someone applies SUBSTANTIAL pedal pressure. The key is to ONLY open the bleeder far enough to cause the light to go out, and NOT far enough to create a pressure imbalance in the opposite direction, thereby tripping the light switch again.

vdubstreets · 12-13-2009, 10:07 PM

I'll see if i can get the GF to help me this weekend with that. I was driving it really for the first time tonight and thought the rear's were locking up a little hard. Maybe I'm just not used to non-anti lock brakes since i haven't driven the YJ in a while either. But I'll try bleeding it first.

skyway0018746 · 12-15-2009, 05:59 PM

yeah something is wrong, rear brakes on the xj dont work that good.

macman043 · 01-11-2010, 05:47 PM

Actually try looking under the dash by the brake pedal for a white box with a pin like switch and a wire on it leading to somewhere i don't know, the brake is supposed to press it when your not using the brakes... keeping the lights off. This is where my issue is, but now i can't figure out how to get that switch back in place.

vdubstreets · 01-12-2010, 12:20 PM

Thanks I'll take a look, i still have a feeling its a uneven pressure issue discussed above.

vdubstreets · 02-11-2010, 10:39 PM

for those of you curios, turns out my wheel cylinder was bad and finally just gave out.

**Mickey_D** · 02-12-2010, 12:13 AM

Quote:

Originally Posted by macman043

Actually try looking under the dash by the brake pedal for a white box with a pin like switch and a wire on it leading to somewhere i don't know, the brake is supposed to press it when your not using the brakes... keeping the lights off. This is where my issue is, but now i can't figure out how to get that switch back in place.

Wrong brake light. He's talking about the warning light on the dash, not the external lights...