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TROUBLESHOOTING
SYMPTOM
High head - low suction
High head - high or normal suction
Low head - high suction
Unit will not run
Condenser fan runs,
compressor doesn't
Low suction - cool compressor
Iced evaporator coil
Compressor short cycles
Registers sweat
High suction pressure
Insufficient cooling
POSSIBLE CAUSE
a. Restriction in liquid line or
TXV not functioning
a. In Cooling: Dirty condenser coil
In Heating: Dirty filter, Dirty indoor coil
b. Overcharged
c. In Cooling: Condenser fan not running
c. In Heating: Indoor blower not running
a. Incorrect TXV.
b. Defective compressor valves
c. TXV not functioning properly
d. Incorrect TXV setting
a. Power off or loose electrical connection
b. Thermostat out of calibration set too high
c. Defective contactor
d. Blown fuses or tripped breaker
e. Transformer defective
f. High or low pressure control open
(Optional)
g. Compressor overload contacts open
a. Loose connection
b. Compressor stuck, grounded or open
winding open internal overload
c. Low voltage connection
d. Capacitor weak, open, or shorted
a. In Cooling: Low indoor airflow
In Heating: Dirty outdoor coil, defective
defrost thermostat, defective defrost
control board, outdoor fan not running, low
refrigerant charge.
b. Low airflow
c. Low refrigerant charge
d. Operating unit in cooling mode below 65°F
outdoor temperature
a. Defective overload protector
b. Unit cycling on low pressure control
c. High pressure switch cuts out
a.
Low airflow
a. Excessive load
b. Defective compressor
c. Reversing valve not seating properly.
a. Improperly sized unit
b. Improper airflow
c. Incorrect refrigerant charge.
d. Incorrect voltage
REMEDY
a. Remove or replace with proper size TXV.
a. Clean coil
b. Correct System charge
c. Repair or Replace
a. Replace with correct TXV
b. Replace compressor
c. Check for debris in TXV or deformed TXV.
Remove debris or replace TXV.
d. Check Super Heat
a. Check for unit voltage at contactor in unit
b. Reset
c. Check for 24 volts at contactor coil replace if
contacts are open
d. Replace fuse or reset breaker
e.
Check wiring - replace transformer
f. Check high pressure control or check unit
charge
High pressure control opens at 610 psig
Low pressure control opens at 22 psig
g. Replace compressor
NOTE: Wait at least 2 hours for overload to reset
a. Check for unit voltage at compressor check &
tighten all connections
b. Wait at least 2 hours for overload to reset If still
open, replace the compressor.
c. At compressor terminals, voltage must be within
10 % of nameplate volts when unit is operating
d. Check capacitor. If defective, replace.
a.
Increase speed of blower or reduce restriction -
replace air filters
b. Check - should be approximately 400 CFM per
ton, dirty air filters, all duct outlets open
c. Properly charge unit
d. Install or check low ambient control, should be
open below 65°F outdoor temperature
a. Replace - check for correct voltage
b. Check refrigerant charge and / or airflow
c. Check airflow (indoor & outdoor),
check expansion device
a. Increase speed of blower or reduce restriction
replace air filters
a. Recheck load calculation
b. Replace
c. Replace
a. Recalculate load
b. Check - should be approximately 400 CFM per ton
c. Charge per procedure attached to unit service
panel
d. At compressor terminals, voltage must be within
10% of nameplate volts when unit is operating
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