New Holland CX720 Repair Manual page 1306

Alternator - Testing (A.30.A.82 - G.40.A.20)
NOTE: The batteries must be fully charged and all connections clean and tight. Use a multimeter (DVOM) for these
tests. For battery testing and service, see the battery section in the service manual.
DO NOT use a self-powered test light for any of these tests. Use of a self-powered light can cause damage
to components in this system. M979
Before performing any of the electrical tests, be sure all operating controls are in neutral or park lock position.
This will eliminate accidental movement of the machine or start-up of power driven equipment. M980
N° Test Point
1 Place transmission in PARK.
Start engine and set at 1200 rpm.
Measure voltage at battery.
2 Place negative lead of DVOM to
Battery positive terminal and posi-
tive lead to starter B+ terminal.
Read voltage.
3 Attach positive lead of DVOM to B+
terminal of Alternator and negative
lead to starter B+ terminal.
Read voltage.
4 Measure for 12 volts at the B+ ter-
minal of the Alternator, while turning
various load on and off (lights, heater
fans etc.)
5 Stop engine, Ignition Switch in "OFF"
position.
Measure resistance between Alter-
nator housing and engine ground.
Alternator - Testing (A.30.A.82 - G.40.A.20)
NOTE: The batteries must be fully charged and all connections clean and tight. Use a multimeter (DVOM) for these
tests. For battery testing and service, see the battery section in the service manual.
DISTRIBUTION SYSTEMS - ELECTRICAL POWER SYSTEM
12.8-14.5 volts.
If good reading, charging system is
operating properly.
Less than 0.4 volts.
If good reading, circuit is good.
Go to next test point.
Less than 0.4 volts.
If good reading, go to next test point.
Voltage varies between 12.8 - 14.5
volts in response to load applied.
If good reading, charging system is
operating properly
Less than 1 ohm.
If good reading, repair or replace Al-
ternator.
CAUTION
WARNING
Expected Result
2 4/7/2006
A.30.A / 1126
Other Result (Possible Cause)
High resistance between Battery and
B+ terminal at Alternator.
Go to next test point.
High resistance between Battery and
starter B+ terminal.
Repair/replace wiring as needed.
High resistance in circuit 802 (RD).
Repair/replace wiring as needed.
Alternator
Go to next test point.
High resistance on circuit 803 (BK)
from Alternator to engine ground.
Clean surfaces at Alternator and
engine block. Ensure that all mount-
ings are clean and tight.