TEST OR INSPECTION
APU - CONT
BATTERY WILL NOT HOLD CHARGE - CONT
Using an electrical tester (multimeter) (item 17, appx. B) on
appropriate setting to read 1k - 1.4k resistance, check current
limiter for conductivity by tagging, disconnecting, and probing
three current limiter leads in APU control box:
1k - 1.4k
If results are different than specified above, remove and
APU CHARGING CIRCUIT FAILS TO KEEP BATTERY CHARGED
Check that battery will hold a charge.
Refer to symptom 12, step 1, and check that battery will hold a
APU must be allowed to run for several minutes for charging circuit to stabilize;
otherwise, indications measured may not be accurate.
(multimeter) (item 17, appx. B) on a 29 Vdc setting or greater,
measure battery voltage by placing negative (-) probe on
battery ground post (-) and placing positive (+) probe on
battery positive (+) post.
Check that battery voltage (with APU running) measures 13 Vdc
2 Vdc. If battery voltage measures less than 11 Vdc, check
fan dynamo ac output by disconnecting leads from dynamo and
measuring minimum of 13 Vac between each of two yellow leads
and red lead. If voltages are not present, shut down APU and
present, proceed to step 3, and check bridge rectifier.
4-30 Change 2