Midtronics VAS 6161, Instruction Manual, Page: 25 / 41

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Chapter 6: System Test
Starter decision
Average cranking
voltage
Cranking time in
milliseconds
X axis = time
Alternator Test
1. ANALYZING CHARGING SYSTEM DATA: After you press the NEXT soft key to begin the alternator
test, the Tester will immediately begin testing for alternator voltage.
2. TURN ALL VEHICLE LOADS OFF, IDLE ENGINE: Turn off vehicle loads (blowers, interior light, radio,
etc.) and idle the engine. Press the
NEXT soft key to continue.
NOTE: If necessary the analyzer will ask if you are testing a diesel engine. It will resume
testing after you make your selection.
3. REV ENGINE WITH LOADS OFF FOR 5 SECONDS: Rev the engine with the loads off. Gradually
increase the rpm until the analyzer tells you to HOLD the rev level as the bar on the display
crosses the rpm target line.
4. ACQUIRING DATA....HOLD ENGINE RPM: Continue to hold the rpm while the Tester takes system
measurements.
5. ENGINE REV DETECTED, IDLE ENGINE: The Tester has detected the rev. Press the NEXT soft key to
continue.
6. TESTING ALTERNATOR AT IDLE, LOADS OFF: The analyzer will next test the engine at idle for
comparison to other readings, and then test the diode ripple. Excessive ripple usually means one
or more diodes have failed in the alternator or there is stator damage.
7. TURN HIGH BEAMS AND BLOWER MOTOR ON, IDLE ENGINE: After a few seconds, the Tester will
ask you to turn on the accessory loads. It will determine if the charging system is able to provide
enough current for the demands of the electrical system.