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TROUBLESHOOTING & REPAIR
F-40 F-40
RANGER 305D
ROTOR RESISTANCE AND GROUND TEST (STATIC) (continued)
FIGURE F.9 – ROTOR BRUSH LEADS
SLIP RINGS
BRUSHES
LEADS
201
5H
+
-
LEADS
200A
200
TEST PROCEDURE
1. Turn the engine off.
2. Perform the Case Cover Removal proce-
dure.
3. Locate and label the four leads from the rotor
brush holder assembly. See Figure F.8.
Using the needle nose pliers, remove the
leads. This will electrically isolate the rotor
windings.
4. Using the ohmmeter, check the rotor winding
resistance across the slip rings. See Figure
F.9. Normal resistance is approximately 4.7
*ohms, at 77 degrees Fahrenheit.
(25degreesC.).
5. Measure the resistance to ground. Place
one meter probe on either of the slip rings.
Place the other probe on any good unpaint-
ed chasms ground. The resistance should
be very high, at least 500,000 (500k) ohms.
6. If the test does not meet the resistance spec-
ifications, then the rotor may be faulty and
should be replaced.
7. If this test meets the resistance specifica-
tions, continue testing using the dynamic
rotor resistance and ground test.
