Carrier 38AUZ Installation, Start-Up And Service Instructions Manual page 24

PROBLEM
COMPRESSOR CYCLES ON LOW-PRESSURE SWITCH
Indoor-Air Fan Running
1. Liquid line solenoid valve(s) fails to open.
2. Filter drier plugged.
3. Expansion valve power head defective.
4. Low refrigerant charge.
Airflow Restricted
1. Coil iced up.
2. Coil dirty.
3. Air filters dirty.
4. Dampers closed.
Indoor-Air Fan Stopped
1. Electrical connections loose.
2. Fan relay defective.
3. Motor overload open.
4. Motor defective.
5. Fan belt broken or slipping.
COMPRESSOR RUNNING BUT COOLING INSUFFICIENT
Suction Pressure Low
1. Refrigerant charge low.
2. Head pressure low.
3. Air filters dirty.
4. Expansion valve power head defective.
5. Indoor coil partially iced.
6. Indoor airflow restricted.
Suction Pressure High
1. Unloaders not functioning
2. Heat load excessive.
UNIT OPERATES TOO LONG OR CONTINUOUSLY
1. Low refrigerant charge.
2. Control contacts fused.
3. Air in system.
4. Partially plugged expansion valve or filter drier.
SYSTEM IS NOISY
1. Piping vibration.
2. Compressor noisy.
COMPRESSOR LOSES OIL
1. Leak in system.
2. Crankcase heaters not energized during shutdown.
3. Improper interconnecting piping design.
FROSTED SUCTION LINE
Expansion valve admitting excess refrigerant.
HOT LIQUID LINE
1. Shortage of refrigerant due to leak.
2. Expansion valve opens too wide.
FROSTED LIQUID LINE
1. Restricted filter drier.
2. Liquid line solenoid valve partially closed.
TROUBLESHOOTING (cont)
1. Check liquid line solenoid valve(s) for proper operation. Replace if
necessary.
2. Replace filter drier.
3. Replace power head.
4. Add charge. Check low-pressure switch setting.
1. Check refrigerant charge.
2. Clean coil fins.
3. Clean or replace filters.
4. Check damper operation and position.
1. Tighten all connections.
2. Replace relay.
3. Power supply.
4. Replace motor.
5. Replace or tighten belt.
1. Add refrigerant.
2. Check refrigerant charge. Check outdoor-air fan thermostat settings.
3. Clean or replace filters.
4. Replace power head.
5. Check low-pressure setting.
6. Remove obstruction.
1. Check unloader adjustments. Check unloader setting.
2. Check for open doors or windows in vicinity of fan coil.
1. Add refrigerant.
2. Replace control.
3. Purge and evacuate system.
4. Clean or replace.
1. Support piping as required.
2. Replace compressor if bearings are worn.
1. Repair leak.
2. Check wiring and relays. Check heater and replace if defective.
3. Check piping for oil return. Replace if necessary.
Adjust expansion valve.
1. Repair leak and recharge.
2. Adjust expansion valve.
1. Remove restriction or replace.
2. Replace valve.
24
SOLUTION