TM 9-2330-388-14
(4)
Apply and release the service brake several
times. Listen for immediate response from the relay
valve. If there is hesitation in brake application and re-
lease, replace the relay valve.
b.
Replacement.
(1) Block
semitrailer
wheels
to
prevent
movement.
(2) Disconnect towing vehicle and / or air brake
lines and open air drain valves on bottom of both
reservoirs, fig. 4-54. Leave open while replacing valve.
(3) Tag air lines for identification at assembly.
Disconnect hose and tube fittings from valve. Remove
Figure 4-52. Packing Ring Installation.
double check valve and unscrew valve from nipple in
reservoir.
delivered through the service line to the emergency lay
valve.
(4) Screw new valve into nipple. Install double
check valve, and reconnect hose and tube fittings.
(2)
The emergency relay valve releases air from
primary brake reservoir to the brake chambers to set
(5) Close air drain valves in both reservoirs.
brakes.
Connect towing vehicle and fill the reservoir.
(3)
Engage the service brake and apply so; water to
(6) Test service brakes and parking brakes as
exhaust port on top of the emergency re valve. If there is
described in part a.
leakage, replace the relay valve.
(7) Remove blocking from semitrailer wheels.
4-116