instrument panel--BRAKE LIGHT
 

I did a search, but came up with nothing...

I got a 83 300d.

The brake indicator light on the instrument panel is stuck on.

There is plenty of brake fluid in the master cylinder, front and back.

And the buttons/switches on top of the master brake cylinder, seem to be working fine.

ANY IDEAS ? Thanks.

That light will also indicate if the parking brake is on, make sure it's fully disengaged.

Its quite common for the parking brake pedal to not retract all the way....thus leaving the light on. Its been on in my SD for about 3.5 years now. :o

It burned out in my dad's SD. :D

Could you be referring to the brake pad wear indicator light?

Its not the brake pad light, its the Brake light.

The parking brake pedal, retracts just fine.

Thanks everybody.

Any other ideas ?

That's it basically. There's just the fluid switches and the parking brake switch. Try unplugging them to narrow it down.

http://www.peachparts.com/Wikka/W123BrakeWarningLights

This is the applicable part of the wiring diagram:

It's prolly the parking brake. Even with it fully disengaged over the years the cable can stretch enough so the pedal droops and doesn't engage the switch for the light. Try putting your foot up in front of the pedal and pulling up toward you (the opposite of applying the brake). If the light goes off you've found your problem.

Other than the standard answers for odd light behavior on the instrument cluster: bad ground or a fault/crack in the cluster. That's in the "hard to isolate" electrical fault category.

Try unplugging the wire at the reservoir. That may help isolate if it's a faulty test button or level switch. Then I'd check the switch at the pedal.