PD 4106 1964 mechanic in colorado springs? Air brake issue

[agetme]

Have replaced R12 valve, found air line not connected to foot valve that goes to r12 for brake light switch, still get no air to rear brakes when connected, but brake lights now work. Have air at r12 (supply) but no exhaust or brakes when brake pedal pushed or released.

Bad NEW r12? All tanks have air, when pulled release valves on tank do vent air.

Have manual, at this point feeling dumb as I have exp as mechanic (aircraft) but am at a place where I need to get a mechanic. Close to Colorado springs or castle rock.

thanks,

Tom Hamilton

[wildbob24]

Tom,

It sounds like the control line from the treadle valve is not connected to the relay valve. In the original 4106 installation, there was a "T" fitting at the relay with the switch on top and the line from the treadle in the side. That control line from the treadle should be operating the switch and the relay valve at the same time.

Bob