Thermo King 914970, Manual

Page: 84 / 186

Electrical Maintenance
84
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. Set the unit for Continuous Run operation and
place the On/Off switch in the Off position.
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 2 circuit.
5. Set the unit for continuous run operation and
place the main On/Off switch in the On
position.
6. Wait 20 seconds for the unloading timer to
de-energize the unloading relay and 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 run it in high speed.
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 Regulator
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.