Carrier 38AU - Manual (Page 35)

35
TROUBLESHOOTING (cont)
PROBLEM SOLUTION
COMPRESSOR RUNNING BUT COOLING INSUFFICIENT
Suction Pressure Low
1. Refrigerant charge low.
1. Add refrigerant.
2. Head pressure low. 2. Check refrigerant charge. Check outdoor-air fan thermostat settings.
3. Air filters dirty. 3. Clean or replace filters.
4. Expansion valve power head defective. 4. Replace power head.
5. Indoor coil partially iced. 5. Check low-pressure setting.
6. Indoor airflow restricted. 6. Remove obstruction.
Suction Pressure High
1. Unloaders not functioning
1. Check unloader adjustments. Check unloader setting.
2. Heat load excessive. 2. Check for open doors or windows in vicinity of fan coil.
UNIT OPERATES TOO LONG OR CONTINUOUSLY
1. Low refrigerant charge.
1. Add refrigerant.
2. Control contacts fused. 2. Replace control.
3. Air in system. 3. Purge and evacuate system.
4. Partially plugged expansion valve or filter drier. 4. Clean or replace.
SYSTEM IS NOISY
1. Piping vibration.
1. Support piping as required.
2. Compressor noisy. 2. Replace compressor if bearings are worn.
COMPRESSOR LOSES OIL
1. Leak in system.
1. Repair leak.
2. Crankcase heaters not energized during shutdown. 2. Check wiring and relays. Check heater and replace if defective.
3. Improper interconnecting piping design. 3. Check piping for oil return. Replace if necessary.
FROSTED SUCTION LINE
Expansion valve admitting excess refrigerant.
Adjust expansion valve.
HOT LIQUID LINE
1. Shortage of refrigerant due to leak.
1. Repair leak and recharge.
2. Expansion valve opens too wide. 2. Adjust expansion valve.
FROSTED LIQUID LINE
1. Restricted filter drier.
1. Remove restriction or replace.
2. Liquid line solenoid valve partially closed. 2. Replace valve.