Carrier 38AU - Manual (Page 34)

34
TROUBLESHOOTING
PROBLEM SOLUTION
COMPRESSOR DOES NOT RUN
Contactor Open
1. Power off.
1. Restore power.
2. Fuses blown in field power circuit. 2. After finding cause and correcting, replace with correct size fuse.
3. No control power. 3. Check control transformer primary connections and circuit breaker.
4. Thermostat circuit open. 4. Check thermostat setting.
5. Safety device lockout circuit active. 5. Reset lockout circuit.
6. Low-pressure switch open. 6. Check for refrigerant undercharge, obstruction of indoor airflow.
Make sure liquid line solenoid valve(s) is open.
7. High-pressure switch open. 7. Check for refrigerant overcharge, obstruction of outdoor airflow, air
in system. Be sure outdoor fans are operating correctly.
8. Compressor overtemperature switch open. 8. Check for open condition. Allow for reset. Replace if defective.
9. Loose electrical connections. 9. Tighten all connections.
10. Compressor stuck. 10. See compressor service literature.
Contactor Closed
1. Compressor leads loose.
1. Check connections.
2. Motor windings open. 2. See compressor service literature.
3. Single phasing. 3. Check for blown fuse. Check for loose connection at compressor
terminal.
COMPRESSOR STOPS ON HIGH-PRESSURE SWITCH
Outdoor Fan On
1. High-pressure switch faulty.
1. Replace switch.
2. Reversed fan rotation. 2. Confirm rotation, correct if necessary.
3. Airflow restricted. 3. Remove obstruction.
4. Air recirculating. 4. Clear airflow area.
5. Noncondensables in system. 5. Recover refrigerant and recharge as required.
6. Refrigerant overcharge. 6. Recover refrigerant as required.
7. Line voltage incorrect. 7. Consult power company.
8. Refrigerant system restrictions. 8. Check or replace filter drier, expansion valve, etc.
Outdoor Fan Off
1. Fan slips on shaft.
1. Tighten fan hub setscrews.
2. Motor not running. 2. Check power and capacitor.
3. Motor bearings stuck. 3. Replace bearings.
4. Motor overload open. 4. Check overload rating. Check for fan blade obstruction.
5. Motor burned out. 5. Replace motor.
COMPRESSOR CYCLES ON LOW-PRESSURE SWITCH
Indoor-Air Fan Running
1. Liquid line solenoid valve(s) fails to open.
1. Check liquid line solenoid valve(s) for proper operation. Replace if
necessary.
2. Filter drier plugged. 2. Replace filter drier.
3. Expansion valve power head defective. 3. Replace power head.
4. Low refrigerant charge. 4. Add charge. Check low-pressure switch setting.
Airflow Restricted
1. Coil iced up.
1. Check refrigerant charge.
2. Coil dirty. 2. Clean coil fins.
3. Air filters dirty. 3. Clean or replace filters.
4. Dampers closed. 4. Check damper operation and position.
Indoor-Air Fan Stopped
1. Electrical connections loose.
1. Tighten all connections.
2. Fan relay defective. 2. Replace relay.
3. Motor overload open. 3. Power supply.
4. Motor defective. 4. Replace motor.
5. Fan belt broken or slipping. 5. Replace or tighten belt.