Proceed to perform the troubleshooting procedure steps.
Figure 36 will assist you in locating the terminals, leads, wires, etc.,
that are involved in troubleshooting the APU starting system.
Figure 12, page 16, of this subcourse, will assist you in tracing the APU
APU starting system.
You complete the preliminary checks and the APU engine still will not crank
when you operate the starting switch.
The first test is to determine if
power is flowing from lead 49 of wiring harness 12330257 to the lead 66 of
wiring harness 12330248.
APU Electrical Harnesses.
Perform the test as follows:
Test 1. Disconnect the main harness connector from the APU wall-
mounted receptacle. Place the multimeter red probe on terminal A
of the receptacle and ground the black probe.
Set the MASTER
switch to the ON position and check for voltage. If voltage is
indicated, go to Test 2.
If no voltage is indicated, check
voltage at lead 66, harness 12330248 and lead 49, harness