TM 5-3805-262-20
3-19. AIR BRAKE SYSTEM TROUBLESHOOTING (CONT)
MALFUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
3. LOW AIR PRESSURE (AIR PRESS GAGE INDICATES IN RED ZONE AND LOW AIR PRESSURE
BUZZER SOUNDS) (Cont).
S t e p 1 1 . ( C o n t ).
a .
b.
c.
(Cont).
Hold cap to prevent movment and tighten nut against cap. Check
and be sure air is still flowing from loosened tube fitting.
Tighten loosened tube fitting at tee.
Disconnect shop compressed air system hose from elbow installed
in pressure protection valve.
Loosen and remove 9/16-18 pipe plug installed in hose.
Reconnect and tighten hose fitting to elbow installed in pres-
sure protection valve .
Close air reservoir drain valve.
If air does not flow from loosened tube fitting, hold cap and
loosen nut.
Turn cap counterclockwise until air just starts flowing from
l o o s e n e d t u b e f i t t i n g.
Hold cap to prevent it from moving and tighten nut against cap.
Check and be sure air is still flowing from loosened tube fit-
t i n g .
Tighten loosened tube fitting at tee.
Disconnect shop compressed air system hose from elbow installed
in pressure protection valve.
Loosen and remove 9/16-18 pipe plug installed in hose.
Reconnect and tighten hose fitting to elbow installed in pres -
sure protection valve .
Close air reservoir drain valve.
If pressure protection valve cannot be adjusted, replace it
(page 7-64).
Step 12. Open air reservoir drain valve to drain air.
At declutch treadle and valve, loosen and disconnect parking brake
v a l v e h o s e f r o m s t r a i g h t f i t t i n g .
Install a 7/16-20 cap on straight fitting and a 7/16-20 plug in
hose .
Close air reservoir drain valve.
Start engine and operate at 1000 rpm.
See if air pressure is normal.
Shut off engine.
a. If air pressure is normal, open air reservoir drain valve to
d r a i n a i r .
Remove 7/16-20 cap and plug from straight fitting and hose.
3-126
