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TROUBLESHOOTING AND DIAGNOSTICS
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. Alarm tripped. 3. Check alarm history on HSIO.
4. No control power. 4. Check secondary fuse(s); replace with correct type and size. Re-
place transformer if primary windings receiving power.
5. Compressor circuit breaker tripped. 5. Check for excessive compressor current draw. Reset breaker; re-
place if defective.
6. Safety device lockout circuit active. 6. Reset lockout circuit at HSIO or circuit breaker.
7. Low-pressure switch open. 7. Check for refrigerant undercharge, obstruction of indoor airflow, or
whether compressor suction shutoff valve is fully open. Make sure
liquid line solenoid valve(s) is open.
8. High-pressure switch open. 8. Check for refrigerant overcharge, obstruction of outdoor airflow, air in
system or whether compressor discharge valve is fully open. Be sure
outdoor fans are operating correctly.
9. Loose electrical connections. 9. Tighten all connections.
10. Compressor stuck. 10. See 06E compressor service literature.
Contactor Closed
1. Compressor leads loose. 1. Check connections.
2. Motor windings open. 2. See 06E 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. Airflow restricted. 2. Remove obstruction.
3. Air recirculating. 3. Clear airflow area.
4. Noncondensables in system. 4. Purge and recharge as required.
5. Refrigerant overcharge. 5. Purge as required.
6. Line voltage incorrect. 6. Consult power company.
7. Refrigerant system restrictions. 7. Check or replace filter drier, expansion valve, etc. Check that com-
pressor discharge valve is fully open.
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. Filter drier plugged. 1. Replace filter drier.
2. Expansion valve power head defective. 2. Replace power head.
3. Low refrigerant charge. 3. 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.
LEGEND
HSIO — Human Sensory Input/Output Device
DSIO — Processor Module
VFD — Variable Frequency Drive
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