TROUBLESHOOTING 777 SERVICE MANUAL
10-28 Published 10-01-2012, Control # 045-08
TESTING
Test 1 – Battery Test (12 and 24 VDC)
To test the 12 VDC accessory system voltage using a digital
multimeter, record the voltage before and during cranking. A
voltage reading of 12 volts or less before cranking may
indicate a charging system fault. A drop of 4 volts or more
indicates the battery is failing.
Test the 12 VDC starting batteries connected in series for 24
volts using a digital multimeter, record voltage before and
during cranking. A voltage reading of 24 volts or less before
cranking may indicate a charging system fault. A drop of 8
volts or more during cranking indicates a failing battery.
Item Description Item Description
1 Positive probe 2 Negative probe
2
1
AA301
12 VDC
FIGURE 10-1
AA302
24 VDC
1
2
FIGURE 10-2
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