Thermo King 919180, Manual

Page: 52 / 148

Electrical Maintenance
52
1. Press the
O
FF
key to make sure the unit is
turned Off.
2. 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.
3. Check the voltage at the B+ terminal on the
alternator. Battery voltage must be present. If
not, check the 2A circuit.
4. Check the voltage at the VOLT SENSE
terminal on the alternator. Battery voltage
must be present. If not, check the SENS
circuit.
5. Use the Service Test mode to place the unit in
high speed cool before the engine starts. See
the
µ
P-T Microprocessor Diagnosis Manual
for information about the Service Test mode.
6. Check the voltage at the EXC terminal on the
alternator. Battery voltage must be present. If
not, check the EXC circuit.
7. Attach a clamp-on ammeter to the 2A wire
connected to the B+ terminal on the alternator.
8. Connect a voltmeter between the B+ terminal
and a chassis ground.
9. Start the unit and use the Service Test mode to
place the unit in high speed cool. See the
µ
P-T
Microprocessor Diagnosis Manual, for
information about the Service Test mode.
10. 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.
Excessive Voltage Output
12 Volt Alternators With Internal Regular Setting:
When a Thermo King unit is installed on a truck,
it is often connected to a truck battery. When both
the Thermo King unit and the truck engine are
running on the truck battery, the charging system
with the higher voltage may automatically turn off
the charging system with the lower voltage
output.
If it is determined that the Thermo King regulator
setting is higher than the truck charging system or
the batteries are consuming more water than
normal the following solution may help solve the
problem.
• Remove the wire labeled SENSE and tape
off.
• Add a jumper wire from 2A to the SENSE
terminal on the back of the alternator.
This should reduce the voltage to the battery by
0.2 to 0.3 of a volt.
CAUTION: Never apply battery voltage to
terminal F2 or voltage regulator failure
will occur.