How to reset brake combination valve?

[njsteve]

Ran into a dilemma yesterday. I was installing the new repro bleeder master cylinder and couldn't get the combination valve to reset in order to get fluid to the back brake circuit. Driving the car onto the trailer with the rear brake line unhooked (though plugged) set off the BRAKE indicator light.

I tried everything: cracking a front bleeder and keeping the rears shut, then stepping on the brakes only resulted in the dash light turning out, indicating that the valve reset, but it must be internally blocked since the reset pin was still sticking out and no fluid was moving the the rear. I then put a plug into the rear circuit port of the valve to provide something for the fluid to press against and build internal pressure - once again the ligh would reset but no valve movement. Finally I just said the heck with it and removed the valve and put in a spare that I luckily had sitting on the shelf.

Anyone have any idea how to reset the valve? I tried removing the indicator plug with the electrical lead from the top, and manually moving the slider valve in the tiny port it engages with, but no luck there either - the slider wouldn't move. Pushing on the metal indicator stem doesn't budge it either.