1. Close start or disconnect switch.
2. Replace fuse.
3. Refer to electrical section.
4. Repair or replace control.
5. Relocate control.
6. Check wiring against diagram.
7. Replace or relocate.
8. Trace control circuit with wiring diagram and repair.
9. Replace the compressor with all precautions.
1. Line disconnect switch open.
2. Fuse removed or blown.
3. Overload protector tripped.
4. Control stuck in open position.
5. Control off due to cold location.
6. Wiring improper or loose.
7. Thermostat defective or improperly installed.
8. Control circuit open.
9. Burned/open circuit motor winding.
Compressor will not start – no hum.
TROUBLE SHOOTING CHART
SYMPTOM
CAUSES
CHECK & CORRECTIVE MEASURE
1. Additional current passing through overload pro-
tector.
2. Low voltage to unit (or unbalanced if three
phase).
3. Overload protector defective.
4. Excessive discharge pressure.
5. Suction pressure too high.
6. Compressor too hot - return gas hot.
7. Compressor motor has a winding shorted.
1. Check wiring diagram. Check for added fan motors,
pumps, etc. connected to wrong side of protector.
2. Determine the reason and correct.
3. Check current, replace protector.
4. Check airflow across the condenser coil, re-
strictions in refrigeration system.
5. Check for possibility of misapplication. Use stronger unit.
6. Check refrigerant charge (fix leak), add if necessary.
7. Replace compressor.
1. Check wiring against diagram.
2. Determine reason and correct.
3. Replace compressor.
4. Replace compressor.
5. Check crankcase heater.
6. Unequalized pressure in the system.
1. Improperly wired.
2. Low voltage to unit.
3. Compressor motor has a winding open or
shorted.
4. Internal mechanical trouble in compressor.
5. Liquid refrigerant in compressor.
6. High discharge pressure.
Compressor starts and runs, but short
cycles on overload protector.
Compressor will not start – hums but
trips on overload protector.
Units runs OK, but short cycles on.
1. Check the cause.
2. Differential set too close - widen.
3. (a) Check airflow to the condenser - correct.
(b) Reduce refrigerant charge.
(c) Purge.
4. (a) Fix leak, add refrigerant.
(b) Replace device.
1. Overload protector.
2. Thermostat.
3. High pressure cut-out due to:
(a) Insufficient air.
(b) Overcharge.
(c) Air in system.
4. Low pressure cut-out due to:
(a) Undercharge.
(b) Restriction in expansion device.
Unit operates long or continuously.
1. Shortage of refrigerant.
2. Control contacts stuck or frozen closed.
3. Refrigerated or air conditioned space has ex-
cessive load or poor insulation.
4. System inadequate to handle load.
5. Evaporator coil iced.
6. Restriction in refrigeration system.
7. Dirty condenser.
8. Filter dirty.
1. Fix leak, add charge.
2. Clean contacts or replace control.
3. Determine the fault and correct.
4. Replace with larger system.
5. Defrost.
6. Determine location and remove.
7. Clean condenser.
8. Clean or replace.
Suction line frosted or sweating.
1. Expansion valve passing excess refrigerant or
is oversized.
2. Expansion valve stuck open.
3. Evaporator fan not running.
4. Overcharge of refrigerant.
1. Re-adjust valve or replace with smaller valve.
2. Clean valve of foreign particles, replace if nec-
essary.
3. Determine reason and correct.
4. Correct charge.
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