GR8-1200 OEM
Midtronics Inc. 7000 Monroe Street Willowbrook, IL 60527
www.midtronics.com
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Table 13: Charging System Decisions
Charging System
Decision
Action
NO PROBLEMS
The system is showing normal output from the alternator. No problem detected.
NO VOLTAGE
The alternator is not providing charging voltage to the battery.
√
Check the belts to ensure the alternator is rotating with the engine running. Replace broken or
slipping belts and retest.
√
Check all connections to and from the alternator, especially the connection to the battery. If the
connection is loose or heavily corroded, clean or replace the cable and retest.
√
If the belts and connections are in good working condition, replace the alternator. (Older vehicles
use external voltage regulators, which may require only replacement of the voltage regulator.)
LOW VOLTAGE
The alternator is not providing enough voltage to power the system’s electrical loads and charge the
battery.
√
Check the belts to ensure the alternator is rotating with the engine running. Replace broken or
slipping belts and retest.
√
Check the connections from the alternator to the battery. If the connection is loose or heavily
corroded, clean or replace the cable and retest.
HIGH VOLTAGE
The voltage output from the alternator to the battery exceeds the normal limits of a functioning regulator.
√
Check to ensure there are no loose connections and that the ground connection is normal. If there
are no connection problems, replace the regulator. (Most alternators have a built-in regulator
requiring you to replace the alternator. In older vehicles that use external voltage regulators, you
may need to replace only the voltage regulator.)
The regulator controls voltage output based on the battery voltage, under-hood temperature, and
vehicle loads used. In other words, it controls the maximum voltage the system can produce based
on the current needs and amount of current that can be produced by the spinning of the rotor in the
alternator. The normal high limit of a typical automotive regulator is 14.5 volts +/–0.5. Refer to the
manufacturer speci
fi
cations for the correct limit, which may vary by vehicle type.
A high charging rate will overcharge the battery and may decrease its life and cause it to fail. If the
battery test decision is REPLACE and the charging system test shows a HIGH OUTPUT, check the
battery’s electrolyte levels. A symptom of overcharging is battery
fl
uid spewing through the vent caps,
which causes low electrolyte levels and will harm the battery.
Diode Decision
Action
EXCESSIVE RIPPLE
One or more diodes in the alternator are not functioning or there is stator damage, which is shown by
an excessive amount of AC ripple current supplied to the battery.
√
Make sure the alternator mounting is sturdy and that the belts are in good shape and functioning
properly. If the mounting and belts are good, replace the alternator.
OPEN PHASE
The analyzer has detected an open phase within the alternator. Replace the alternator.
OPEN DIODE
The analyzer has detected a open diode within the alternator. Replace the alternator.
SHORTED DIODE
The analyzer has detected an shorted diode within the alternator. Replace the alternator.
Chapter 6: System Test
