brake light issure

OK i have a 72 c10 that i just put a new master cylinder on and i dont know how to reset the proportioning valve ****on or whatever its called. any help on that would be appreciated. thanks

 

just unscrew the switch from the prop valve, this will centralise the valve ,and screw it back in.

 

If I'm not mistaken the GM valves are supposed to be spring centered. If the light is staying on the switch in the middle of the valve may be stuck to one side. Loosen a line on one end and pump the brake pretty hard. If that doesnt turn the light out loosen a line on the other side of it and pump it agian.

 

And sometimes, if it is stuck hard enough, it takes proper application of hammer to shake it loose.

 

Nooooo!!!
the light switch has the spring in it. When one side of the system loses pressure the centralising rod that the switch is sitting against is pushed to one end of the valve body and the switch rod drops off into a step. it cant re-centralise itself until the switch is removed. then the valve will centralise and the switch light stays off. Using a BFH is not the answer.

 

I had one stick like that, I had to remove the proportion valve and bang it on a wood work bench to get it to move, once it broke free, I centered it and put a bolt in place of the switch, bled the brakes without worry, then reinstalled the switch. good luck

 

Hook up a test light to the switch post on the prop. valve-one side of the light to hot and the other to the contact on the valve. If the light is on, the valve is not centered. Try bleeding the furtherst bleeder from the master and see if you get flow. If you do not get flow, close that bleeder and go to the front side of the system. Open a bleeder and have a helper slowly push down on the brake pedal until the light goes out, then close the bleeder valve. The pressure diferential valve is now centered and you should be able to bleed the brakes normally.

 

ok thanks guys. i appreciate it.