TM 55-1520-240-T 12-3.4  FIRE EXTINGUISHING SYSTEM OPERATIONAL CHECK (Continued) 12-3.4 TASK RESULT 1. Check that  ENGINE NO.  1 FIRE EXT circuit If FIRE EXT circuit breaker (1) is open, close it.  If it breaker (1) is closed. opens again, go to task 12-3.5. 2. Check that  ENGINE NO.  2 FIRE EXT circuit If FIRE EXT circuit breaker (2) is open, close it.  If it breaker (2) is closed. opens again, go to task 12-3.5. 3. Tag and disconnect two wires (3 and 4) from each cartridge (5) on fire extinguishers (6). CAUTION Make sure wire terminal lugs do not touch cartridge terminals or fuse- lage.  Aircraft damage or fire extin- guisher discharge could occur. CAUTION Do not connect multimeter to car- tridge.  This could discharge extin- guisher agent or reduce cartridge life. 4. Connect multimeter, set to measure 28 VDC, between wires W668-68-20(+) and W668- GD125A20N(-) at forward cartridge (5) on No.  1 fire extinguisher (6). 5. Pull out NO.  1 ENGINE fire handle (7). 6. Set and hold FIRE EXT AGENT switch (8) to Multimeter shall indicate 28 VDC.  If not, go to task BOTTLE NO.  1. 12-3.6.  If voltage is present and trouble symptom, Fire extinguisher No.  1 did not discharge on No.  1 engine, was reported, replace forward cartridge (5) on No.  1 fire extinguisher (6). 7. Release FIRE EXT AGENT switch (8). 8. Disconnect multimeter.  Connect multimeter to wires W668-69-20 (+) and W668- GD246A20N (-) at forward cartridge (5) on No.  2 fire extinguisher (6). 9. Set and hold FIRE EXT AGENT switch (8) to Multimeter shall indicate 28 VDC.  If not, go to task BOTTLE NO.  2. 12-3.7.  If voltage is present and trouble symptom, Fire extinguisher No.  2 did not discharge on No.  1 engine, was reported, replace forward cartridge (5) on No.  2 fire extinguisher (6). 10.  Release FIRE EXT AGENT switch (8). 11.  Push in NO.  1 ENGINE fire handle (7). 12.  Pull out NO.  2 ENGINE fire handle (9). 13.  Disconnect multimeter.  Connect multimeter to wires W666-64-20 (+) and W666- GD247A20N at aft cartridge (5) on No.  1 fire extin- guisher (6). TASK RESULT 14.  Set and hold FIRE EXT AGENT switch (8) to Multimeter shall indicate 28 VDC.  If not, go to task BOTTLE NO.  1. 12-3.8.  If voltage is present and trouble symptom. Fire extinguisher No.  1 did not discharge on No.  2 engine, was reported, replace aft cartridge (5) on No.  1 fire extinguisher (6). 15.  Release FIRE EXT AGENT switch (8). 16.  Disconnect multimeter.  Connect multimeter to wire W666-63-20 (+) and W666- GD124A20N at aft cartridge (5) on No.  2 fire extin- guisher (6). 17.  Set and hold FIRE EXT AGENT switch (8) to Multimeter shall indicate 28 VDC.  If not, go to task BOTTLE NO.  2. 12-3.9.  If voltage is present and trouble symptom. Fire extinguisher No.  2 did not discharge on No.  2 engine, was reported, replace aft cartridge (5) on No.  2 fire extinguisher (6). 18.  Release FIRE EXT AGENT switch (8). 19.  Push in NO.  2 ENGINE fire handle (9). CAUTION Insure wires are connected to right terminals on cartridge.  Reverse con- nections will prevent agent release when a fire occurs.  Ground wire must be connected to terminal on side of cartridge. 20.  Connect two wires (3 and 4) to each cartridge (5) on fire extinguishers (6).  See tags and wiring diagram (12-3.2).  Remove tags. FOLLOW-ON MAINTENANCE: Perform operational check of engine fuel shutoff valves. TM 55-1520-240-23: Battery Disconnected Electrical Power Off END OF TASK Change 12  12-59