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3. After allowing time for the regulator’s start-up delay, place the head of a steel screwdriver near the nut on the
pulleyshaft or near the rear bearing of the alternator. There should be substantial magnetic pull. If a magnetic
field is present, the voltage regulator, alternator brushes and rotor are likely to be working properly.
If there is little or no magnetic pull at the pulley shaft or at the rear bearing, initiate the following test:
With the key off and the engine off, remove the large harness plug from the
regulator.
1. Insert the end of a short length of electrical wire to the RED connector
slot of the regulator harness and the other end of the wire to the BLUE
connector slot. This bypasses the regulator and tests the alternator and
the harness.
2. Using your steel screwdriver, inspect for a magnetic field as described
above.
3. With your voltmeter, check for voltage on the blue wire at the alternator. If
voltage does not exist, the harness may be at fault. If voltage does exist
at the harness, but no magnetism is present, the alternator is likely to be
malfunctioning.
4. If a magnetic field is present. Both harness and alternator brushes and rotor appear to be working properly. If
no magnetic field is present, proceed with the next test.
Testing the actual output of the alternator is known as “Full Field Testing”. This can be accomplished by jumping a
positive 24VDC current to the field terminal at the rear of the alternator. This test eliminates both the regulator and the
harness, making it easier to isolate your investigation to the alternator.
CAUTION: Ensure that all voltage sensitive equipment is turned off prior to starting the engine. Voltage is
unregulated during this test and could damage sensitive electronics. DO NOT let the engine run any longer
than necessary to detect charging. If the system is not charging, remove the alternator and have it inspected
by a qualified alternator shop, or call Balmar for warranty evaluation.
To test the alternator:
1. Clip a jumper wire to the positive post of the alternator, or on the battery side of the isolator (if an isolator is in
use). Use a SHIELDED alligator clip for post attachment. Unintentional contact between the alligator clip and
the alternator case could result in damage to your electrical system.
2. Disconnect the field wire from the rear of the alternator and attach the other end of the jumper wire to the
alternator’s Field terminal (F). CAUTION: Do not allow the wire to contact the case while it is attached to the
positive post. The case is grounded and severe damage could occur.
3. The regulator is now bypassed. When the ignition is engaged and the motor is started, the voltage should rise
and charging current should be present.
4. The motor should be run long enough to determine that charging voltage is present. Unregulated voltage can
rise quickly. Do not allow extended unregulated charging to occur without carefully monitoring voltage levels.
If the alternator fails to generate voltage during field testing, a malfunction of the alternator is likely. Contact
your local alternator repair shop or Balmar’s technical service staff for recommendations.
Conclusion
If your readings differ substantially from the “Expected Readings” listed in the troubleshooting charts, the regulator
may be malfunctioning, or there may be a continuity problem. Contact our technical support staff at (360) 435-6100.
If you determine that repair service is necessary for either your alternator or regulator, please gather the following
information before contacting our service technicians: Make and model of alternator. Model of voltage regulator and
date of mfg. (date punched on rear side label of regulator). Voltage readings on red, brown and blue wire at regulator
with engine off, key on. Voltage readings on red, brown and blue wire at regulator with engine running at a fast ideal
1400 rpm.
Alternator Testing Continued
