Parking Brake Light - stays slightly on, kills battery

[KiwiWagoneer]

Hi there,
Looking for some advice on where to start checking.
I've got a 1990 Jeep Grand Wagoneer that seems to flatten the battery due to a slightly illuminated parking brake light on the dash when the key is removed from the ignition. When the Jeep is on / running, this light is illuminated at 'full' strength, and if the Jeep is parked without the brake being engaged, the light is completely off...
Any ideas where to start cursing at?
Much appreciated...
J

[tgreese]

Not sure about the '90 model, but the earlier models have a switch on the parking brake pedal that grounds a wire to the lamp when the pedal is depressed. That could be partly contacting and showing the bulb dimly all the time. This light also indicates when the master cylinder has a pressure imbalance between the front and rear wheel circuits. This will indicate a brake system failure (or impending failure). Both of these systems should be off (no power) when the ignition is off, so it's hard to see how this could drain the battery.

Really, it's very hard to diagnose electrical problems without the car in front of you. How I would approach this is to look at the wiring diagram from the TSM and see what could possibly be causing power to this bulb all the time. Then I would use my multimeter (or test light) and trace those circuits to localize the fault. Without the car to test, you're just guessing.

[ShagWagon]

Seems like bad/dirty pedal switch and bad ignition switch at a glance.

All dash lights should turn off with key in the off position.