B contacts of relay K2
Battery
Indicator light DS6
Circuit breaker CB1
DC starter-generator G3
Circuit breaker CB2
DC voltage regulator VRl
Reverse current relay K6
Resistor R3
Starter dropout relay K7
6-6. If fuel supply problems are encountered, first check switch SI, and then check
the boost pump for proper operation.
6-7. If the fuel control system does not operate correctly, carefully check the func-
tion of each APU control component and the corresponding relay contacts in the con-
sole.
APU Components
Relay and Contacts
Fuel pressure switch
K1, contacts A, B, C, D
Hour meter
K2, contacts A, B, C, D
Ignition exciter
K3, contacts B
Start fuel valve
K4, contacts B
Main fuel valve
K5, contacts B, C
6-8. Malfunctions are indicated by the low oil pressure indicator light DSl, high ex-
haust indicator light DS2, and overspeed indicator light DS3, and controlled by the fol-
lowing corresponding relay contacts.
Rectifier
Relay & Contacts
CR1
K1, contacts C, D
CR2
K2, contacts A, D
K3, contacts A, D
K4, contacts A, D
K5, contacts A, D
K102
If malfunction circuits indicate faults, or if false APU shutdown occurs, carefully
check all malfunction circuit components.
6-6
