TM 9-2330-294-14
Table 3-2. Troubleshooting Semitrailer Continued
MAI.FUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
Step 2. Brakes not functioning properly.
MALFUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
B R A K E AIR SYSTEM
1.
NO RESPONSE FROM ANY SEMITRAILER BRAKE WHEN BRAKE PEDAL IN
TOWING VEHICLE IS DEPRESSED.
Step 1. Check to see if shutoff valves are closed in towing vehicle service and/or emergency air
lines.
Open shutoff valve.
Step 2. Check to see if intervehicular air hoses are properly connected.
Close shutoff valve in towing vehicle. Disconnect and reconnect air hose. Open
shutoff valve.
2.
ALL SEMITRAILER BRAKES WEAK
Check semitrailer pressure at tank valve on auxiliary air supply valve for required 90-120
psi.
3.
SLOW BRAKE APPLICATION - ALL SEMITRAILER BRAKES
Step 1. Check to see if intervehicular service air hose is properly connected.
Close shutoff valve on towing vehicle. Disconnect and reconnect air hose. Open
shutoff valve.
Step 2. Check to see if shutoff valve is partially closed on towing vehicle service air line.
Open shutoff valve
4.
SLOW BRAKE RELEASE . ALL SEMITRAILER BRAKES
Check to see if intervehicular service air hose is properly connected or service air line
shutoff valve on towing vehicle is partially closed.
Close shutoff valve on towing vehicle. Disconnect and reconnect air hose. Open
shutoff valve.
5.
SLOW BRAKE RELEASE ON ONE OR THE OTHER SEMITRAILER TANDEM.
Visually inspect emergency relay valve vent and see if it is blocked with mud, ice, or other
obstructions.
Clean port.
6.
BRAKES OVERHEAT
Check semitrailer pressure at auxiliary air supply valve using tire gage, 90-120 psi required.
7.
FAIL-SAFE NOT HOLDING
Step 1. Manually release power spring.
CAUTION
If springs are already fully released the release bolt may be against its stop so so not use heavy
force if the bolt will not turn. Excessive force can strip the release bolt.
Turn release bolt counterclockwise until a stop is felt (para 2-3).
Step 2. Check and see if fail-safe manual release valve handle is pushed in.
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