Electrical Maintenance
81
•
No field current or a low field current
indicates an open circuit or excessive
resistance in the field circuit. Remove the
voltage regulator and brush assembly and
inspect the slip rings. If the slip rings and
are acceptable, install a new voltage
regulator and brush assembly and repeat
the test. If the brushes are not the problem,
replace the alternator.
•
High field current indicates a short in the
field circuit. Replace the rotor or the
alternator.
Battery
Inspect/clean the battery terminals and check the
electrolyte level during scheduled maintenance
inspections. A dead or low battery can be the
cause of an ammeter indicating discharge due to
lack of initial excitation of the alternator even
after the unit has been boosted for starting. The
minimum specific gravity should be 1.235. Add
distilled water as necessary to maintain the proper
water level.
Battery Cables
These units use 0-gauge battery cables to ensure
reliable starting in extremely cold weather. Make
sure to use the 0-gauge battery cables when
replacing the battery cables. Refer to the unit Parts
Manual for the correct part numbers.
Battery Charger (Optional)
The optional battery charger replaces the
alternator. The battery charger converts AC power
from the AC generator (or the electric standby
power source) to 12 Vdc to charge the battery and
provide power for the 12 Vdc control system.
NOTE: There are some alarm codes for the
battery charger. Check for alarm codes related to
the battery charger before testing it.
Test the battery charger output as follows:
1. Use the Service Test Mode to run the unit in
high speed cool. Refer to the appropriate
Diagnostic Manual for specific information
about the Service Test Mode.
2. Use the
G
AUGES
key to check the Amps
Display and the Battery Voltage Display. The
Amps reading should show a positive value.
The Battery Voltage reading should increase
slowly until it stabilizes at approximately 14
Vdc. If not, go to the next step.
3. Check for DC voltage Between the BATT and
GND terminals at the battery charger. The
voltage should be within 1 Vdc of the Battery
Voltage reading in step 2. If the voltage is
acceptable, check the 2BC and GND circuits
back to the battery and ground for continuity.
If not, go to the next step.
4. Check for AC voltage between the L1, L2,
and L3 terminals at the battery charger.
Approximately 345 Vac should be present
between each pair. If the voltage is acceptable,
the battery charger is probably faulty. If not,
go to the next step.
5. Check the L1, L2, and L3 circuits (including
any contactors) back to the AC generator for
continuity. If the L1, L2, and L3 circuits all
have good continuity, test the AC generator.
Condenser Fans
There are two condenser fans located near the top
of the unit. Each condenser fan has its own
electric motor and contactor, which allows the
condenser fans to be controlled separately. The
roadside condenser fan rotates counterclockwise
when viewed from the top. It draws air through
the roadside condenser coil and the radiator coil.
It also draws air up through a cooling channel to
cool the battery and optional battery charger. The
curbside condenser fan rotates clockwise when
viewed from the top. It draws air through the
curbside condenser coil. During engine operation
the condenser fan speed varies with the engine
speed.
Test the condenser fans as follows:
1. Use the Service Test Mode to run the unit in
high speed cool. Refer to the appropriate
Diagnostic Manual for specific information
about the Service Test Mode.
2. Use the Service Test Mode to energize
condenser fan you want to test. It should run at
approximately 2700 rpm in the correct
