Thermo King 098916, Maintenance Manual

Page: 158 / 196

Diagnosis: Troubleshooting, Status Messages, Alarm Codes
157
Compressor contactor burned
out
Low line voltage
Increase line voltage to at least 90
percent of compressor motor rating
Excessive line voltage
Reduce line voltage to at least 110
percent of compressor motor rating
Short cycling Eliminate cause of short cycling
Unit short cycles Refrigerant overcharge causing
cycling on high pressure cutout
Purge system
Inefficient condenser operation
causing cycling on high pressure
cutout
Check condenser airflow,
condenser fan motor, condenser fan
grille, condenser fan pressure
switch, water pressure switch
(option), water flow rate (option) and
water-cooled condenser-receiver
tank (option)
Noisy compressor Loose mounting bolts Tighten mounting bolts
Oil slugging or refrigerant flooding
back
Perform controller pretrip test to
check refrigerant charge. Check
expansion valve adjustment. Check
compressor for compressor oil.
Scroll rotating backwards
Check phase correction system and
check unit wiring
Defective compressor Repair or replace compressor
Condenser fan motor does not
operate
Unit in Heat or Defrost
Check indicator lights. If unit is in
Heat or Defrost, unit operation is
normal (no remedy required)
Unit in Cool with Low condenser
temperature
Check indicator lights condenser
temperature and discharge
pressure. Condenser temperature
may not require condenser fan
operation (no remedy required;
condenser fan also pulses on and
off on a 30 second cycle to control
condenser temperature)
Water pressure switch Closed
(Water-cooled position) (Option)
If unit is on water cooled condenser
operation, unit operation is normal.
Otherwise water pressure switch
must be Open for air-cooled
condenser operation.
Defective water pressure switch;
(option)
Replace defective switch
Loose line connection Tighten connections
Open motor internal thermal overload
protector
Check for seized bearings or
defective thermal overload
protector. Repair or replace as
necessary
Defective motor Replace motor
Detective condenser fan contactor Replace defective contactor
No condenser fan output signal from
controller
Diagnose and replace condenser
fan relay, main relay board or
controller
Condition Possible Cause Remedy