TROUBLESHOOTING GUIDE
SYMPTOM
CAUSE
REMEDY
Compressor does not run —
Contactor open
Power off.
Restore power.
Fuses blown.
Replace with correct fuses after finding cause
and correcting.
Transformer open/shorted.
Replace transformer if primary windings are
receiving power and no output.
Thermostat circuit open.
Check thermostat setting.
Low-pressure switch open.
Check for refrigerant undercharge or system
leak.
High-pressure switch open.
Check for refrigerant over charge or
obstruction of outdoor airflow.
Connections loose.
Tighten all connections.
Compressor motor thermostat open.
Check for excessive motor temperature.
Compressor does not run —
Contactor closed
Compressor leads loose, broken.
Check connections with power off.
Single phasing.
Replace blown fuse.
Compressor internal overload open.
Allow compressor motor windings to cool down to reset
overload. Determine cause for overload opening.
Compressor cycles on high-
pressure switch —
Condenser fan on
High-pressure switch faulty.
Replace switch.
Airflow restricted. Dirty coil.
Remove obstruction, clean condenser coil.
Air recirculating.
Clear airflow area.
Noncondensables in system.
Recover, evacuate and recharge as required. Refer to
Carrier GTAC-II, Module 5, Charging, Recovery,
Recycling, and Reclamation.
Refrigerant overcharge.
Recover as required.
Refrigerant system restrictions.
Check or replace filter drier, expansion
valve, etc.
Compressor cycles on high-
pressure switch —
Condenser fan off
Fan slips on shaft.
Tighten fan hub screws.
Motor not running.
Check power and capacitor
1
⁄
3
and
3
⁄
4
hp motor.
Motor bearings seized.
Replace motor.
Motor overload open.
Check overload rating. Check for
fan blade obstruction.
Motor burned out, windings open.
Replace motor.
Compressor cycles on low-
pressure switch —
Evaporator fan running
Filter drier plugged.
Replace filter drier.
Expansion valve power head
defective.
Replace power head.
Low refrigerant charge.
Find leak, repair, evacuate system, and recharge.
Expansion valve restricted/plugged.
Remove and replace expansion valve.
Airflow restricted —
Low suction pressure
Evaporator coil iced up.
Check refrigerant charge.
Evaporator coil dirty.
Clean coil fins.
Indoor-air filter dirty.
Clean or replace filters.
Indoor-air dampers closed.
Check damper operation and position.
Indoor (evaporator) fan stopped —
Low suction pressure
Electrical connections loose.
Tighten all connections.
Fan relay defective.
Replace relay.
Motor overload open.
Check power supply.
Motor defective.
Replace motor.
Fan belt broken or slipping.
Replace or tighten belt.
Compressor runs but
cooling insufficient —
Suction pressure low
Refrigerant charge low.
Add charge.
Head pressure low.
Check refrigerant charge.
Indoor-air filters dirty.
Clean or replace filters.
Expansion valve power head
defective.
Replace power head.
Expansion valve restricted/plugged.
Remove and replace expansion valve.
Evaporator coil partially iced.
Check low-pressure setting.
Evaporator airflow restricted.
Remove obstruction.
Compressor runs but
cooling insufficient —
Suction pressure high
Heat load excessive.
Check for open doors or windows.
NOTE: See Fig. 15 and 16 for component arrangements.
13
