TM 10-7310-241-12&P 4-10.1  TROUBLESHOOTING INSTRUCTIONS FOR MODEL 471012 (Continued) Change 1     4-8.1 Problem Probable cause   Solution Tap leaks:      -at main container outlet. Shank jam nut is loose. Tighten jam nut. Shank O-ring is leaking. Replace O-ring. HWR vents at lid gasket. Lid gasket is leaking. Tighten or replace lid gasket. Pressure relief valve. Valve inlet port is loose. Re-tighten inlet port on underside of lid.      - leaks between lid and   O-ring is leaking. Replace O-ring.        manifold.      - always vents Valve is stuck open. Replace valve.      - allows excessive pressure   Inlet port is blocked, or valve is Clean as required.          build-up dirty.   Relief valves are defective.   Replace relief valve. HWR circuit breaker trips. Heating element is shorting.   Replace heating element. Insulation is wet.   Repair leak. Replace insulation. Thermal switch or thermal   Repair wiring or replace thermal switch switch wiring is shorting. Circuit board is defective   Replace circuit board   HWR heats in OFF (0) position.  HWR power cable is incorrectly Check cable wiring for correct polarity. White light illuminates; green does not. wired (wrong polarity). Pin A is positive and pin B is negative.(Refer to vehicle manual) Rewire as required. HWR heats in OFF (0) position.  Power transistor isolator is Replace isolator. White light illuminates; green does not. (Continued) shorting. Heating element is shorting.   Replace heating element. Insulation is wet.   Repair leak. Replace insulation. Circuit board is defective   Replace circuit board   HWR heats in OFF (0) position.  Switch is defective.   Replace switch. Both lights illuminate. Circuit board is defective. Replace circuit board. HWR does not heat in either Vehicle circuit breaker has Reset breaker. If problem persists,   setting.  Neither light illuminates. tripped. check for shorting. Switch or switch wiring is defective. Rewire or replace switch. Thermal switch or thermal switch Rewire or replace thermal switch. wiring is defective.