AUTOMOTIVE ELECTRICAL CIRCUITS AND WIRING

To calculate charging system output, add the two ammeter readings. This will give you
total charging system output in amps. Compare this figure to the specifications within
the manufacturer's manual.
Current output specifications will depend on the size (rating) of the alternator. A
vehicle with few electrical accessories may have an alternator rated at 35 amps,
whereas a larger vehicle with more electrical requirements could have an alternator
rated from 40 to 80 amps. Always check the manufacturer's service manual for exact
values.
If the charging system output current tested low, perform a regulator voltage test and a
regulator bypass test to determine whether the alternator, regulator, or circuit wiring is
at fault.
Regulator Voltage Test
A regulator voltage test checks the calibration of the voltage regulator and detects a
low or high setting. Most voltage regulators are designed to operate between 13.5 to
14.5 volt range. This range is stated for normal temperatures with the battery fully'
charged. Regulator voltage test procedure is as follows:
Set the load tester selector to the correct position using the manufacturer's manual.
With the load control OFF, run the engine at 2,000 rpm or specified test speed. Note
the voltmeter reading and compare it to the manufacturer's specifications.
If the voltmeter reading is steady and within manufacturer's specifications, then the
regulator setting is okay. However, if the volt reading is steady but too high or too low,
then the regulator needs adjustment or replacement. If the reading were not steady, this
would indicate a bad wiring connection, an alternator problem, or a defective
regulator, and further testing is required.
Regulator Bypass Test
A regulator bypass test is an easy and quick way of determining if the alternator,
regulator, or circuit is faulty. Procedures for the regulator bypass test is similar to the
charging system output test, except that the regulator be taken out of the circuit. Direct
battery voltage (unregulated voltage) is used to excite the rotor field. This should allow
the alternator to produce maximum voltage output.
Depending upon the system there are several ways to bypass the voltage regulator. The
most common ways are as follows:
Sorting a test tab to ground on the rear of the alternator (if equipped).
Placing a jumper wire across the battery and field terminals of the alternator.
With a remote regulator, unplug the wire from the regulator and place a jumper wire
across the battery and field terminals in the wires to the alternator.
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