This is a 72 442 with front disc brakes. The brake light on the dash intermittently glows dimly. It glows with normal brightness when the emergency brake pedal is engaged. All of the brakes are functioning at each wheel and there are no leaks. The car still has the original proportioning valve. What is the cause of this?

I should add that this starting after I flushed the brake lines.

Warren

 

Remove the wire from the combination/proportioning valve and see if the light goes out.

 

Eric has correctly listed the first place to look. If the light stays off with the wire disconnected, the problem is that the piston inside the combo valve is not quite centered. If the light still comes on, the problem could be the switch on the e-brake pedal or an intermittent short in the wire anywhere along it's length. The BRAKE light illuminates when the wire is grounded.

 

If the piston is not centered, is there a way to center it without taking the valve apart? Although I haven't disconnected the wire I suspect that the piston shifted during the process of flushing the lines.

 

A bleeder tool may or a pick may center it, or sometimes pressing the brake pedal hard could drive it over also. You remove the brake light switch and screw this in its place.

 

Well I managed to get the light to turn off in a fairly easy way. I simply tapped the side of the plunger switch and proportioning valve about 30 times. Either the plugger switch was sticking or the tapping centered the piston.

 

Whatever works...