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Howard-McCray A Division of HMC Enterprises, LLC.
831 East Cayuga Street • Philadelphia, PA 19124 USA • (215) 464-6800 • (800) 344-8222
Fax (215) 969-4890 • E-Mail: [email protected] 101018
8
Trouble Chart
A. Compressor will not start - no hum
Possible Causes:
1. Disconnect switch open
2. Blown fuse
3. Defective wiring
4. Overload protector tripped
5. Open control contacts (control may be
defective, or unit location may be too
cold)
6. Defective overload protector
B. Compressor will not start - hums but cycles on
overload
Possible Causes:
1. Low voltage
2. Unit wired incorrectly
3. Starting capacitor defective
4. Starting relay contact not closing
5. Compressor motor defective
6. High head pressure
7. Bearings on pistons tight - low oil charge
C. Compressor starts, but starting winding
remains in circuit
Possible Causes:
1. Low voltage
2. Unit wired incorrectly
3. Starting capacitor weak
4. Running capacitor defective
5. Starting relay defective
6. Compressor motor defective
7. High head pressure
D. Compressor starts and runs but cycles on
overload
Possible Causes:
1. Low voltage
2. Running capacitor defective
3. Overload protector defective
4. High head pressure
5. Fan motor, pump, etc., wired to wrong
side of overload protector
6. Compressor motor partially grounded
7. Unbalanced line voltage (3 phase models)
8. Bearing or pistons tight - low oil charge
E. Compressor short cycles
Possible Causes:
1. Control differential set too close
2. Refrigerant undercharge
3. Refrigerant overcharge
4. Discharge valve leaking
5. Expansion valve leaking
6. Cutting out on high pressure control
7. Cutting out on overload protector because
of tight bearings, stuck piston, high head
pressure or restricted air cooled
condenser
F. Compressor tries to start when thermostat
closes but cuts out on overload, starts after
several attempts
Possible Causes:
1. Low voltage
2. Thermostat differential too close (lower
than 10°)
3. Thermostat bulb not in tight contact with
evaporator
G. Running cycle too long, or unit operated
continuously
Possible Causes:
1. Insufficient refrigerant charge
2. Dirty or restricted condenser
3. Unit: location too hot
4. Control contacts stuck
5. Air or other non-condensable gases in
system
6. Expansion valve plugged or defective
7. Cabinet doors left open too long
8. Insufficient, defective or water - logged
insulation
9. Evaporator coil plugged with ice or dirt
H. Evaporator temperature too high
Possible Causes:
1. Shortage of refrigerant, or leak on system
2. Restricted capillary tube, strainer or drier
3. Control setting too high
4. Expansion valve restricted
5. Expansion valve too small
6. Evaporator coil plugged with ice or dirt
7. Evaporator oil logged
I. Noisy Unit
Possible Causes:
1. Compressor oil charge low
2. Fan blade bent causing vibration
3. Fan motor bearings loose or worn
4. Tube rattle
5. Loose parts on condensing unit
J. Liquid line hot
Possible Causes:
1. Unit undercharged or leak in system
2. Expansion valve opened too far
K. Liquid line frosted
Possible Causes:
1. Restriction in drier
2. Shut off valve on receiver either partially
closed or restricted
L. Suction line sweating or frosted
Possible Causes:
1. Expansion valve open too wide
2. Evaporator iced up
3. Evaporator fan motors not operating
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