Blue Ox BX88143 User Manual
Page 2
Blue Ox Division, Automatic Equipment Mfg. Co. • One Mill Road, Industrial Park
Pender, Nebraska 68047 • Phone 402-385-3051 • Fax 402-385-3360 •
TM
BX88143 is a proportional braking system that can be used on coaches with Total Air or Air
Over Hydraulic braking systems. With the BX88143 you will use your coach’s air brakes by
tapping into the brake relay air source. How ever hard you press on the coach’s brakes, is how
much the towed vehicle’s brakes will be applied.
Locating Air Source On Coach
1. For coaches with total air brake systems, the brake relay is located ahead of the rear axle. This relay
has four to five ports, some of which will be used. There is a right and left brake actuator hose coming from
this relay, these hoses go to the brake actuators of each rear tire of coach. There is a 3/8” O.D. pilot tubing
coming from one of the four ports coming from the brake relay. This is the SERVICE port that is the
preferred place to connect into proportional air that receives pilot air from the coach’s brake pedal. If this
port has a 3/8” hose coming from it, use the furnished tee fitting. Cut the tubing and push the tubing into
each side of the tee fitting, making sure the tubing is bottomed into the fitting. On the bottom of some relay
valves there are four ports, three are used, the other has a 1/2” pipe plug. Remove this plug and install the
furnished 1/2”pipe to 3/8” tube fitting. If your coach needs a fitting that is not supplied, most hardware
stores have brass pipe fittings. There should be no pressure coming from the port, unless the brake pedal is
pushed down. If there is, you need to look for another port. Look at Fig.2 for a detailed schematic.
2. For coaches with air over hydraulic braking systems, the air over hydraulic assembly is located in
front of front axle on the driver’s side. There is a drain plug on the bottom side of the air actuator, take this
plug out and use the supplied tube connector. Look at Fig.3 for a detailed schematic.
3/8” Tubing Installation On Coach
Push the supplied 3/8” DOT tubing into the tee fitting or the pipe to tube fitting making sure it is
bottomed into the port. Route and secure the 3/8” DOT tubing with the 13” nylon ties supplied making sure
to route away from hot parts. There is 50 ft. of tubing supplied, which should be plenty for most coaches.
Once you get to the rear of the coach with the tubing, secure the mount bracket with the 1/4” bolts, flat and
lockwashers in a convenient location on the bumper. Make sure it is the one with the larger hole. Then
mount the bulkhead fitting, 3/8 tube fitting, and QD coupler to this mount bracket as shown in Fig.7. Cut
the extra 3/8” DOT tubing off and then push into the pipe to tube fitting.
1/4” Tubing Installation On Towed
Unplug the QD plug and 1/4” bulkhead fitting from the self-coil hose assembly. If you have a Blue
Ox baseplate you can use the bracket plate to mount to your baseplate with existing bolts. Then mount
the QD plug and 1/4” bulkhead fitting to this bracket as shown in Fig.7.
If you have a baseplate other than a Blue Ox, you can use the other angle bracket supplied.
Mount this bracket with the 1/4” bolts, flat and lockwashers, and hex nuts to your baseplate. Then
mount the QD plug and 1/4” bulkhead to this bracket. Route the 1/4” tubing through the driver’s
side engine compartment using the supplied wire ties, making sure not to run tubing along hot
parts. Push tubing through an existing grommet through the firewall. If there isn’t a hole, drill a
new hole. Route the tubing to the brake pedal, making sure to leave enough to hook to the
pull cylinder that will be mounted to the brake arm. Cut the excess tubing off.
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