Carrier 50JS - Manual (Page 24)

Table 5—Cooling and Heating 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 thermostat, contactor, transformer, con-
trol relay or defrost board
Replace component
Insufficient line voltage Determine cause and correct
Incorrect or faulty wiring Check wiring diagram and rewire correctly
Thermostat setting too high
Lower thermostat setting below room tempera-
ture
Units have a 5-min. time delay
DO NOT bypass this compressor time
delay—wait for 5 min. until time-delay relay is
deenergized
Compressor will not start but condenser fan
runs
Faulty wiring or loose connections in compressor
circuit
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 (posi-
tive temperature coefficient) thermistor
Determine cause and replace
One leg of 3-phase power dead
Replace fuse or reset circuit breaker
Determine cause
Low input voltage (20% low) Determine cause and correct
Three-phase scroll compressor (size 030-
060units) makes excessive noise, and there
may be a low pressure differential
Scroll compressor is rotating in the wrong direc-
tion Correct the direction of rotation by reversing the
3-phase power leads to the unit
Compressor cycles (other than normally sat-
isfying thermostat)
Refrigerant overcharge or undercharge
Recover refrigerant, evacuate system, and re-
charge to capacities shown on nameplate
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
Defective thermostat Replace thermostat
Faulty outdoor-fan motor or capacitor Replace
Damaged reversing valve Determine cause and correct
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
Thermostat set too low Reset thermostat
Low refrigerant charge Locate leak, repair, and recharge
Leaking valves in compressor Replace compressor
Frosted coil with incorrect defrost operation
Check defrost time settings
Reset as necessary
Check defrost temperature switch
Replace as necessary
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
(Heat) Indoor air restricted or recirculating Determine cause and correct
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
Compressor valves leaking Replace compressor
Restriction in liquid tube Remove restriction
Excessive suction pressure
(Heat) Outdoor coil frosted
Move timer on control board to 30 min. between
defrost cycles
(Cool) High Heat load Check for source and eliminate
Compressor valves leaking Replace compressor
Reversing valve hung up or leaking internally Replace valve
Refrigerant overcharged Recover excess refrigerant
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