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« on: May 22, 2013, 12:50:21 pm »
The wire to the combination or proportioning valve detects a shift of the piston caused by a
significant difference in pressure between the front and rear circuits
If you get a little too aggressive with the brake pedal when bleeding the brakes, the valve sees
this as a brake line failure and the piston shifts to shut of that circuit.
That way you would still have good enough brakes to get to a stop.
The only way I know to get the piston back in place is to remove the switch
and pry the piston back into center.
You can confirm that is the problem by checking to see if your rear brakes are working correctly.
I am not sure this is your problem but it reminds me of what I went through some years ago.