CHARGING SYSTEM SERVICE MANUAL NUMBER 22
Page 4B-12 90-860074--1 FEBRUARY 2002
Excitation Circuit
1. Connect positive (+) voltmeter lead to tie strap/terminal on alternator and negative (–)
lead to a ground terminal on alternator (Test 1).
2. Turn ignition switch to RUN position and note voltmeter reading. Reading should be 1.3
to 2.5 volts.
3. If no reading is obtained, an opening exists in alternator excitation lead or in excitation
circuit of regulator. Unplug PURPLE lead from regulator. Connect positive voltmeter
lead to PURPLE lead and negative voltmeter leads to ground (Test 2). If voltmeter now
indicates approximate battery voltage, voltage regulator is defective and the alternator
must be replaced. If no voltage is indicated, check excitation circuit for loose or dirty
connections or damaged wiring.
4. If reading is between .75 and 1.1 volts, rotor field circuit probably is shorted or grounded.
5. If reading is between 6.0 and 7.0 volts, rotor field circuit probably is open.
72785
TEST 1 TEST 2
a
b
c
d
e
a-Excitation Wire - PURPLE
b-Sensing Wire - RED or GREEN
c-Tie Strap/Terminal
d-Voltmeter (0-20 Volts)
e-Ground
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