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Problem Probable Cause Solution
Compressor Will
Not Start
Power o, loose electrical connections or
fuse open
Check disconnect switch, fuses and wiring
Compressor contactor not closing
Check voltage to contactor coil, transformer
slave relay, thermostat
Internal compressor thermal overload open
If compressor is hot, allow 2 hours to cool –
see below
Compressor defective
Check compressor for electrical failure
Compressor may be seized, check for LRA
High or low pressure switch open
or defective
Check calibration of high or low
pressure switch
Oil pressure control open or defective Check oil failure control – see below
Compressor
Starts But Cuts
Out On Low
Pressure Switch
Low on refrigerant Check sightglass and check pressures
Airflow restricted
Check for dirty evaporator coil, dirty filters,
dampers closed, iced evaporator, VFD
settings, check motor amps, duct design
Restriction in liquid line
Check head pressure, check and adjust TXV
if not functioning properly, check pressure
drop across filter drier
Defective low pressure switch Check calibration of switch
Compressor
Starts But Cuts
Out On High
Pressure Switch
Refrigerant overcharged Check pressures, charge by subcooling
Condenser fan control has incorrect setting
Check calibration of the low
ambient control
Fan motor defective Check fan motor
Condenser coil inlet obstructed or dirty
Check coil and inlet clearances and for
possible air re-circulation
Air or non-condensables in system
Compare liquid refrigerant pressure with
the saturated pressure If the presence of
air or non-condensables is suspected, the
refrigerant must be reclaimed through
a service port The system must then be
re-evacuated to 250-500 microns and
recharged The filter-drier should also be
replaced be charging
Defective high pressure switch Replace switch
Restriction in discharge or liquid line
Check discharge and liquid line pressures,
check TXV
Table 13.2: Compressor
PR Series Installation, Operation, and Maintenance Manual
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