Carrier 38AUZ*07 Series Installation, Start-Up And Service Instructions Manual page 74

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