Thermo King 920000, Manual

Page: 60 / 190

Electrical Maintenance
60
6. Place the On/Off switches in the On position
and press the
O
N
key.
7. Check for battery voltage at the 7KB wire in
the main wire harness. If battery voltage is not
present or if it is low, check the 7KB circuit
and the other circuits and components back to
the battery for bad connections or opens.
8. Press the
O
FF
key.
9. Connect the unloading timer wires to the main
wire harness at the two pin connector. Attach
one lead of a voltmeter to the ORG wire and
attach the other lead to the BLU wire.
10. Press the
O
N
key and check the voltage
between the ORG and BLU wires. No voltage
or very low voltage should be present when
the
O
N
key is first pressed. Approximately 20
seconds after the
O
N
key is pressed, battery
voltage should appear between the ORG and
BLU wires. If battery voltage is present when
the
O
N
key is first pressed, or if battery voltage
does not appear approximately 20 seconds
after the
O
N
key is pressed, the unloading
timer is defective and must be replaced.
11. Press the
O
FF
key, replace the
CYCLE-SENTRY module, and connect the
20 wire to the engine reset switch after
completing the test.
Control Circuit Fuse
The control circuit fuse protects the electrical
system if a circuit breaker fails to open. If the fuse
burns out, check for a grounded 2 wire or for any
of the conditions that would cause one of the
circuit breakers to open. Replace the defective
circuit breaker and replace the fuse. The fuse is
located between the battery and the unit control
circuits (typically stored inside the battery box).
Defrost System
Each evaporator should be run through a Defrost
cycle during After Start Inspections and during
scheduled maintenance inspections to test the
Defrost system components. To check the Defrost
cycle, run the evaporator on Cool and set the
thermostat to drop the evaporator coil temperature
below 42 F (6 C). Press the
M
ANUAL
D
EFROST
key.
The evaporator should shift from the Cool cycle
to the Defrost cycle.
If the evaporator continues to Cool, double check
the evaporator coil temperature and refer to the
Defrost Cycle Checkout Procedure.
The air switch setting should be checked annually.
Refer to “Air Switch Testing and Adjustment” on
page 66.
CAUTION: This unit is equipped with
Auto Start. It will start automatically if the
O
N
key is pressed while the On/Off
switches are in the On position.
CAUTION: CYCLE-SENTRY Equipped
Units—Place the Auto Start/Stop -
Continuous Run switch in the Cont Run
position before performing any diagnosis
and service operations on the unit. The
unit may start at any time without prior
warning if the
O
N
key has been pressed
while the On/Off switches are in the On
position and the Auto Start/Stop -
Continuous Run switch is in the
CYCLE-SENTRY position.