I am installing a Roadmaster Brakemaster system on our 1995 U320. I've searched Foreforums for detailed information on where to install the new air line from the air brake relay valve (labeled "SPS valve on Foretravel's drawing) above the rear axle that will go back to the Readybrake connector without success. The picture shows the relay. Currently one hose from port 21 goes to the left rear service brake and one hose from port 22 goes to the right rear service brake. I plan to connect the new Readybrake line to a currently-capped port 22. Also—does anyone recognize the manufacturer of my air relay valve? All comments are appreciated!
Are there any lines in the back of that valve? If not that isn't a relay valve. Relay valves have a tank pressure port, treadle valve port and brake line or lines port.
Yes. There are lines on the upper side (as mounted) of the valve. There is a large line going to port 1 from the air tank and there are two small lines. I think one small one is the control line and I'm not certain about the other small one. Ports 21 and 22 go to the service brake cans on the left and right side respectively. There are separate lines from a different valve going to the spring brake cans.
That would be the relay valve. The control line is hiding in the dirt behind the incoming air line from the pressure tank.