Carrier 48XL - Manual (Page 34)

Table 9 - Troubleshooting Chart
SYMPTOM CAUSE REMEDY
Compressor and outdoor fan
will not start
Power failure Call power company
Fuse blown or circuit breaker tripped Replace fuse or reset circuit breaker
Defective contactor, transformer, control relay, or high-
pressure, loss-of-charge or low-pressure switch
Replace component
Insufficient line voltage Determine cause and correct
Incorrect or faulty wiring Check wiring diagram and rewire correctly
Ul setting too low/too high Reset Ul setting
Units have a 5-minute time delay
DC NCT bypass this compressor time
delay-wait for 5 minutes until time-delay
relay is de-energized
Compressor will not start but condenser fan
runs
Faulty wiring or circuit
Loose connections in compressor
Check wiring and repair or replace
Compressor motor burned out, seized, or
internal overload open
Determine cause
Replace compressor
Defective run capacitor, overload, or PTC (positive
temperature coefficient) thermistor
Determine cause and replace
Low input voltage (20 percent low) Determine cause and correct
Compressor cycles (other than normally sat­
isfying) cooling/heating calls
Refrigerant overcharge or undercharge
Recover refrigerant, evacuate system, and re­
charge to capacities shown on rating plate
Defective compressor Replace and determine cause
Insufficient line voltage Determine cause and correct
Blocked outdoor coil Determine cause and correct
Defective run/start capacitor, overload or start relay Determine cause and replace
Faulty outdoor fan motor or capacitor Replace
Restriction in refrigerant system Locate restriction and remove
Compressor operates continuously
Dirty air filter Replace filter
Unit undersized for load Decrease load or increase unit size
Ul temperature set too low Reset Ul setting
Low refrigerant charge Locate leak, repair, and recharge
Air in system
Recover refrigerant, evacuate system, and re­
charge
Outdoor coil dirty or restricted Clean coil or remove restriction
Excessive head pressure
Dirty air filter Replace filter
Dirty indoor or outdoor coil Clean coil
Refrigerant overcharged Recover excess refrigerant
Air in system
Recover refrigerant, evacuate system, and re­
charge
Indoor or outdoor air restricted or air short-cycling Determine cause and correct
Head pressure too low
Low refrigerant charge Check for leaks, repair and recharge
Restriction in liquid tube Remove restriction
Excessive suction pressure
High heat load Check for source and eliminate
Reversing valve hung up or leaking internally Replace valve
Refrigerant overcharged Recover excess refrigerant
Suction pressure too low
Dirty air filter Replace filter
Low refrigerant charge Check for leaks, repair and recharge
Metering device or low side restricted Remove source of restriction
Insufficient coil airflow Check filter-replace if necessary
Temperature too low in conditioned area Reset Ul setting
Outdoor ambient below 55"'F (13"'C) Verify low-ambient cooling enabled in Ul
Filter drier restricted Replace
IFM does not run
Blower wheel not secured to shaft Properly tighten blower wheel to shaft
Insufficient voltage at motor Determine cause and correct
Power connectors not properly sealed Connectors should snap easily; do not force
IFM operation is intermittent
Water dripping into motor Verify proper drip loops in connector wires
Connectors not firmly sealed
Gently pull wires individually to be sure they are
crimped into the housing
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