Troubleshooting guide

30
www.bendix.com 1-800-AIR-BRAKE (1-800-247-2725)
Tractor Protection Valves
Tractor Protection Valves
The primary function of tractor protection valves (e.g.
the TP-3
™
tractor protection valve) is to protect
the tractor air brake system under trailer breakaway
conditions and/or conditions where severe air leakage
develops in the tractor or trailer. In addition, in
everyday use, the valve is used to shut off the trailer
service and supply lines before disconnecting the tractor
from the trailer. The valve is usually mounted at the
rear of the tractor cab and a dash mounted control
valve.
The TP-3DC
™
tractor protection valve integrates
the functions of the TP-3
™
valve and one double check
valve. A stop light switch port is provided and is
connected to the delivery of the internal double check
valve. It also has an internal single check valve that
prevents air pressure from being trapped in the trailer
service line, which prevents brake compounding and
minimizes roll away conditions.
The TP-4
™
and TP-5
™
tractor protection valves
are designed to incorporate several pneumatic control
functions within a common housing, thereby eliminating
considerable interconnection piping.
These include a combination of two double check valves
and a tractor protection valve. With these valves, either
brake circuit on the vehicle can be used to apply the
trailer brakes. In addition, when used in conjunction
TP-4
™
Tractor
Protection Valve
TP-5
™
Tractor
Protection Valve
TP-3DC
™
Tractor
Protection
Valve
with a control valve, it opens and closes the trailer
service and supply lines in the same manner as a tractor
protection valve. The valves also incorporate porting
for the installation of the service stop lamp switch.
The TP-4
™
tractor protection valve, used solely on Ford
"L" model tractors, incorporates porting for a front
axle limiting control on pre-FMVSS 121 vehicles.
The TP-5
™
tractor protection valve also incorporates
a quick release valve for the trailer service line.
TP-3
™
Tractor
Protection
Valve
SL-5 Stop Light Switch
™
PP-7 Trailer Supply
™
Existing Park Control
Existing Brake Valve
From Rear Axle Service Reservoir
From Front Axle Service Reservoir
To the Tractor Spring Brakes
Supply Hose to Trailer
Service Hose to Trailer
TP-5 Tractor Protection
™
Hose Couplings
Dummy Hose
Coupling
From Double Check (Supplied by Front & Rear Service Reservoir)
Front Axle Delivery
Rear Axle Delivery
D
D
C