Thermo King SB-210, Manual

Page: 70 / 159

Electrical Maintenance
70
• Make sure the drive belts and pulleys of the
charging system are in good condition and are
adjusted properly before testing the alternator.
Worn belts and pulleys or loose belts will
lower the output of the alternator.
• The battery must be well charged, the battery
cable connections must be clean and tight, and
the 2A and excitation circuits must be
connected properly.
NOTE: All voltage readings should be taken
between the negative battery terminal, or a good
chassis ground, and the terminals indicated,
unless stated otherwise.
1. Check to make sure that the F4 fuse is in place
on the interface board. If not, it must be
installed in order for the alternator to charge
properly.
2. Press the
O
FF
key to turn the unit off.
3. Check the battery voltage. If the battery
voltage is less than 12 volts, the battery must
be charged or tested to determine if it should
be replaced.
4. Check the voltage at the B+ terminal on the
alternator. Battery voltage must be present. If
not, check the 2A circuit.
5. Check the voltage at the VOLT SENSE
terminal on the alternator. Battery voltage
must be present. If not, check the 2 circuit.
6. Press the
O
N
key to turn the unit on. Access
the Service Test Mode screens in the
Maintenance Menu before the unit starts.
Energize the run relay in the interface board
test. See the appropriate Diagnostic Manual
for specific information about the Service Test
Mode.
7. Check the voltage at the EXC terminal on the
alternator. Battery voltage must be present. If
not, check the EXC circuit.
8. Attach a clamp-on ammeter to the 2A wire
connected to the B+ terminal on the alternator.
9. Connect a voltmeter between the B+ terminal
and a chassis ground.
10. Start the unit and run it in high speed.
11. Connect a jumper wire between the F2
terminal and a chassis ground. This will full
field the alternator.
a. Full alternator output (the alternators rated
output) indicates the alternator is good but
the voltage regulator needs replacement.
b. If there is LOW or NO output, the
alternator is probably faulty. However, the
following items are potential causes for
not charging:
• Check the alternator brushes.
• Check the 2A circuit from the
alternator to the battery.
• Properly tension the alternator belt.
• Check battery cable connections and
the alternator ground. They must be
clean and tight.
• The battery must be in good condition
and must accept a charge.
• Check for excessive or unusual
amperage draw by the unit control
circuits.
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.
Unit Wiring
Inspect the unit wiring and the wire harnesses
during scheduled maintenance inspections for
loose, chaffed or broken wires to protect against
unit malfunctions due to open or short circuits.
CAUTION: Never apply battery voltage to
terminal F2 or voltage regulator failure
will occur.