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Table 22 — 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 over-temperature switch open. 8. Check for open condition. Allow for reset. Replace compressor if necessary.
9. Loose electrical connections. 9. Tighten all connections.
10. Compressor stuck. 10. See compressor service literature.
11. Fan fault or shutdown condition in fan coil unit active, prevent-
ing thermostat signals passing from fan coil unit to 38AU.
11. Reset fan limit switch (40RF) or address fault in VFD (40RU) or other shutdown
condition.
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. Non-condensables 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
a
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.
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. Heat load excessive. 1. Check for open doors or windows in vicinity of fan coil.
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