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Chapter 7: System Test EXP-800
Charging System Test
When you press NEXT in any test result screen, the analyzer
proceeds to the Charging System Test.
1. CHECKING FOR ALTERNATOR OUTPUT: The analyzer is test-
ing for alternator voltage.
2. TURN ALL VEHICLE LOADS OFF, IDLE ENGINE: Turn o ve-
hicle 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 o. Gradually increase the rpm until
the analyzer tells you to HOLD the rev level as the bar on
the display moves to the right.
NOTE: Some 8-cylinder and older vehicles idle at
a high level after starting, allowing the analyzer
to detect the rev automatically.
4. ACQUIRING DATA....HOLD ENGINE RPM: Continue to hold
the rpm while the analyzer takes system measurements.
5. ENGINE REV DETECTED, IDLE ENGINE: The analyzer has de-
tected the rev. Press the NEXT soft key.
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 alter-
nator or there is stator damage.
7.
TURN HIGH BEAMS AND BLOWER MOTOR ON, IDLE EN-
GINE: After a few seconds, the analyzer 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.
IMPORTANT: Turn on the high-beam headlights and the blower
to high. Do not use cyclical loads such as air condition-
ing or windshield wipers.
8. TESTING ALTERNATOR AT IDLE, LOADS ON: The analyzer
will determine if the charging system is able to provide
sucient current for the demands of the vehicle’s electri-
cal system.
9. REV ENGINE WITH LOADS ON FOR 5 SECONDS: The ana-
lyzer will test the charging system with the loads on and
prompt you to rev the engine. Gradually increase the rev
until the analyzer tells you to HOLD the rev level as the bar
on the display moves to the right.
10. ACQUIRING DATA....HOLD ENGINE RPM: Continue to hold
the rpm while the analyzer takes system measurements.
11. ENGINE REV DETECTED, IDLE ENGINE: The analyzer has de-
tected the rev. Press the NEXT soft key.
12. ANALYZING CHARGING SYSTEM DATA: The analyzer is
completing its nal analysis of the charging system data.
13. TURN OFF LOADS AND ENGINE: Press the NEXT soft key
to display the results. See Table 5 on the next page for an
explanation for the test decisions.
NOTE: When the option TRACK CALLS is enabled,
the EXP writes the results to the data card.
Charging System Test Results
Alternator
decision
Loads-off
DC voltage
at rev
Loads-on
DC voltage
at rev
Normal DC
voltage
range
Bar graph
showing
DC voltage
within
normal
range with
loads on and
off
Graph
of diode
waveform
Peak-to-
peak AC
voltage
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