CHAPTER 2: VEHICLE MAINTENANCE INSTRUCTIONSTM 9-2350-256-202-19 ELECTRICAL TROUBLESHOOTING-ContinuedAPU LOW OIL PRESSURE SYSTEM-ContinuedWARNINGRemove all jewelry such as rings, dogtags, bracelets, etc. If jewelry contacts ametal surface a direct short may result ininstant heatingof tools, damage toequipment, and injury or death topersonnel.KPlace a jumper wire from wire 27 to terminal of LOWOIL PRESS lamp. Place red lead of multimeter onterminal of lamp and black lead to ground. TurnMASTER and APU FUEL SHUTOFF switches on andcheck for voltage. Turn MASTER and APU FUELSHUTOFF switches OFF. If voltage is present,repair/replace wire 420A of APU control box wiringharness (see paragraph 13-7). If voltage is notpresent, replace lamp socket (see paragraph 13-7).LInstall APU control box (9), four screws (8), fourlockwashers (7), and four nuts (6) to mounting bracket.Reconnect APU control box to foot dimmer switch andbulkhead wiring harness to APU control box.Disconnect bulkhead to APU, master relay, and rigger'slights wiring harness from bulkhead disconnect. Placered lead of multimeter on pin C of wire 420A and blacklead to ground. Turn MASTER and APU FUELSHUTOFF switches ON and check for voltage. TurnMASTER and APU FUEL SHUTOFF switches OFF. Ifvoltage is present, go to step M. If voltage is notpresent, repair/replace wire 420A of APU control box tofoot dimmer switch and bulkhead wiring harness (seeparagraph 6-79 for dual voltage; 6-80 for singlevoltage).2-180
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