Table 4-2. Unit Troubleshooting-continued -706880186

TM 5-4210-233-14&P-1

Table 4-2 Unit Troubleshooting - Continued

MALFUNCTION

TEST OR INSPECTION

CORRECTIVE ACTION

FIREFIGHTING SYSTEM - Continued

DISCHARGE HOSE WON'T DE-PRESSURIZE

Check drain valve for blockage.

Clean dirt/blockage from drain hole.

NO FOAM DISCHARGE AT ANY NOZZLE

Step 1. Check if foam valve set OPEN.

Set foam valve to OPEN.

Step 2. Check if foam proportioning valve (in cab or on structural panel) closed.

Set foam proportioning valve to required percentage.

Step 3. Check if foam tank empty or content diluted.

Drain tank and/or refill tank as required.

EXCESS FOAM FROM NOZZLE

Check percentage setting on foam metering valve with chart.

Reset from metering valve. If condition continues, refer to Direct Support Maintenance.

FOAM ENTERING WATER TANK

Check if tank fill/recirculating valve is open or partially open.

Close valve.

WATER ENTERING FOAM TANK

Defective 1-1/2" check valve in foam system piping.

Replace 1-1/2" check valve (see para 4-37).

4-57