Jeep Wrangler TJ dash brake light problem

[Wingman]

Never had this issue before today and thought someone else might benefit from my search.  It was quite puzzling because I had not disturbed any wiring to cause a short.  Fluid was within specs.  Brakes seemed to work as they should and parking brake was better than ever, of course.  Thought it was simple maintenance...

Rig:
2003 Jeep Rubicon, no ABS

Symptoms:
Dash brake warning light illuminated, blinking and audible warning beep when moving.  ANNOYING!

History:
Completed some preventative maintenance/cleaning/adjusting on the rear parking brake mechanism. Processed involved removal of rear calipers from rotors necessitating slight compression of each caliper piston (fluid being forced backward through system).

Solution:
Checked parking brake lever switch with test light = Pass
Checked parking brake lever circuit with test light = Fail/closed circuit
Checked combination (proportioning) block/valve switch = Pass
Checked combination block/valve shuttle = Fail/out of alignment

Corrected shuttle position with small pick and re-installed switch. All back to normal!

Note: removal of the proportioning block switch does not cause fluid loss.


Credit to Jeep Forum for the information!

[MrMindless]

Very interesting! I've never seen the switch fail like that. Given the symptoms I'd have placed a large bet on the parking brake switch.


Tapatalking in traffic

[Wingman]

Me too.  But it wasn't the switch that failed.  It was the differential plunger inside the prop valve that stuck.  Never even knew that was in there...

I'm guessing that if one side (front/back) goes dry, it causes a pressure difference and throws the switch.

[MrMindless]

That exactly why it's for. You'll see that the first time you hit the brakes after losing a line.


Tapatalking in traffic