Carrier 48TC series, Service And Maintenance Instructions, Page: 23 / 112

23
TROUBLESHOOTING THE COOLING SYSTEM
Refer to Table 5 for additional troubleshooting topics.
Table 5 — Cooling Service Troubleshooting
PROBLEM CAUSE REMEDY
Compressor and Condenser 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, or
control relay.
Replace defective 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 temperature.
Compressor Will Not Start But
Condenser Fan Runs
Faulty wiring or loose connections in compressor
circuit.
Check wiring and repair or replace. Tighten loose
connections.
Compressor motor burned out, seized, or internal
overload open.
Determine cause. Replace compressor.
Defective run/start capacitor, overload, start relay. Determine cause and replace defective component.
One leg of three-phase power dead.
Replace fuse or reset circuit breaker. Determine
cause.
Compressor Cycles (other than
normally satisfying thermostat)
Refrigerant overcharge or undercharge.
Recover refrigerant, evacuate system, and recharge
to values on nameplate.
Defective compressor. Replace defective compressor.
Insufficient line voltage. Determine cause and correct.
Blocked condenser. Determine cause and correct.
Defective run/start capacitor, overload, or start relay. Determine cause and replace.
Defective thermostat.
Replace thermostat.
Faulty condenser-fan motor or capacitor. Replace. Defective fan motor or capacitor.
Restriction in refrigerant system. Locate restriction and remove.
Compressor Operates Continuously
Dirty air filter. Replace filter.
Unit undersized for load. Decrease load or replace with larger unit.
Thermostat set too low. Reset thermostat.
Low refrigerant charge. Locate leak; repair and recharge.
Leaking valves in compressor. Replace compressor.
Air in system. Recover refrigerant, evacuate system, and recharge.
Condenser coil dirty or restricted. Clean coil or remove restriction.
Excessive Head Pressure
Dirty air filter. Replace air filter.
Dirty condenser coil. Clean condenser coil.
Refrigerant overcharged. Recover excess refrigerant.
Faulty TXV valve.
1. Check TXV bulb mounting and secure tightly to
suction line and insulate.
2. Replace TXV valve and filter drier if stuck open or
closed.
Air in system. Recover refrigerant, evacuate system, and recharge.
Condenser 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
High head load. Check for source and eliminate.
Compressor valves leaking. Replace compressor.
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.
Faulty TXV valve.
1. Check TXV bulb mounting and secure tightly to
suction line and insulate.
2. Replace TXV valve and filter drier if stuck open or
closed.
Insufficient evaporator airflow.
Increase air quantity. Check filter and replace if
necessary. Check belt tension on blower.
Temperature too low in conditioned area. Reset thermostat.
Outdoor ambient below 25°F. Install low-ambient kit.
Evaporator Fan Will Not Shut Off Time off delay not finished. Wait for 30 second off delay.
Compressor Makes Excessive Noise Compressor rotating in wrong direction. Reverse the 3 phase power leads.