New Holland CX720 Repair Manual page 1301

ELECTRICAL POWER SYSTEM - Problem solving (A.30.A -
G.40.A.30)
OPERATION
Four electrical tests will be required to properly troubleshoot electrical concerns on the combine.
Each test is described in detail. Ensure that all steps are reviewed and followed when testing.
1. Continuity test, short to ground
2. Voltage measurement, short to 12 volts
3. Resistance test for components
4. Continuity test, open circuits
TROUBLESHOOTING
1. ELECTRICAL TEST PROCEDURE 1: CONTINUITY TEST - SHORT TO GROUND CONDITIONS FOR PER-
FORMING TESTS:
1. Power OFF, key switch OFF, (sometimes battery dis-
connected or fuse pulled out if specified in procedure).
2. Connectors at each end or ends of circuit discon-
nected to prevent false readings.
3. Set meter to measure resistance or ohms, and mea-
sure circuit resistance. Use black lead to make contact
with a plated metal part on the chassis such as a jump
start post if fitted. Make sure the surface of the part is
not corroded. Use the red meter lead to touch the con-
nector pins, one pin at a time, and avoid contact with
the case of metal connectors.
4. Determine if measured resistance falls within guide-
lines specified in the procedure. 3 - 4 ohms indicates
a direct short to chassis ground and must be located
and repaired. Higher resistances usually indicate cir-
cuit paths through modules, and that an additional con-
nector needs to be disconnected to perform the test.
More than 100K ohms indicates that the circuit is free
of shorts to ground.
DISTRIBUTION SYSTEMS - ELECTRICAL POWER SYSTEM
55_3_55_3_18
2 4/7/2006
A.30.A / 1121
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