6 Wire Brakeswitch
Before starting: Make
sure your Aux Brake System is in good working order.
This instruction sheet is what is found on most coaches, with electric
engines, and is only to be used as a guide for the installation of
There are several wires in the harness leading to cockpit
exhaust brake switch. There are only 4 wires of interest to us. They
control the operation of the system. These four wires complete two
separate circuits. One circuit is from power supply (IGN switched Buss)
and the other is information from the ECM at the engine. The switch is a
simple double pole single throw switch, which means it is either ON or
OFF, and it controls two circuits.
This is a typical pin socket base on an Aux Brake
Switch. Slots 9 & 10 are perpendicular (commonly used for switch light)
and 1 thru 8 is either blank or horizontal. Most builders use pins 5 and
6 as the connection pins. When information is feed into pin 5 it will
usually come out on pin 1 when switch is turned ON. Information feed
into pin 6 will usually come out on pin 2.
WITH SWITCH ON
With a continuity checker you can check
this. With switch OFF Select Pin 5 NO other pin has continuity, with
switch ON ONLY completed circuit will have continuity. Then select Pin 6
again only the matching pin will complete the circuit.
The color of wires from BrakeSwitch is for connivance only. NOT a
standard color code. The Red and White pairs of wires are to be used to
divert information bound for the cockpit switch into and out of our
control box. Purple was selected to go to brake light source because in
some applications the wire is fed thru a large bundle of other wires and
Purple is very easy to see when close to other wires. (If your coach has
a brake light source in the cockpit use it.) * NOTE [Freightliner
chassis users see Freightliner supplement.] If no source is found in
cockpit we usually go to brake light switch. The brake switches (2) have
power to one side and when brake is applied (power) is then available to
other side of switch. This is where we want to connect to the purple
wire (remember these switches are air switches and air must be up to
complete circuit) NOW connect the black wire to any GOOD ground.
Road Test: speed above 15 MPH apply brakes, your transmission should
shift to lower gear and exhaust brake will close A touch of throttle
will open Exhaust Brake. If you use the Exhaust Brake to reduce speed to
stop the exhaust brake will release around 8 MPH.