CHARGING SYSTEM - 4C-1590-823225--1 1096
Component Testing
ROTOR
1. Test rotor field circuit for opens, shorts or high re-
sistance (Test 1), using an ohmmeter (set on R x1
scale), as follows:
72831
TEST 1 TEST 2
Testing Rotor Field Circuit
a. Connect one ohmmeter lead to each slip ring.
b. Ohmmeter reading should be 4.2 to 5.5 ohms
with rotor at room temperature 70-80°F
(21-26°C).
c. If reading is high or infinite (no meter move-
ment), high resistance or an open exists in
the field circuit. Check for poor connections
between field winding leads and slip ring ter-
minals. If cause for open or high resistance
cannot be found, connect ohmmeter directly
to slip ring terminals. If correct reading is now
obtained, or if reading is still high or infinite,
replace complete rotor assembly.
d. If reading is low, a short exists in the field cir-
cuit. Inspect slip rings to be sure that they are
not bent and touching outer slip ring. Also, be
sure that excess solder is not shorting termi-
nals to aft slip ring. If cause for short cannot
be found, unsolder field winding leads from
slip ring terminals and connect ohmmeter di-
rectly to leads. If correct reading is now ob-
tained, or if reading is still low, slip rings and
rotor field windings are shorted, and com-
plete rotor assembly must be replaced.
73112
b
c
d
a
a - Field Winding Leads
b - Slip Rings
c - Rotor Shaft
d - Pole Pieces
2. Test rotor field circuit for grounds (Test 2), using
an ohmmeter (set on R x1 scale) as follows:
a. Connect one lead of ohmmeter to either slip
ring and the other lead to rotor shaft or pole
pieces.
b. Meter should indicate no continuity (meter
should not move).
c. If continuity does exist, complete rotor as-
sembly must be replaced.
IMPORTANT: If alternator has output at low
speeds, but no output at high speeds, rotor field
winding may be shorting or grounding out, due
to centrifugal force. Replace rotor if all other elec-
trical components test good.
To Next Page
Loading...
