Page 20 GSM-01 081310
Compressor runs, but evaporator does not
1. Faulty blower
motor or broken wire
connection
• Evaporator coil probably frozen
• Shut o power to condensing unit
• Call a CERTIFIED HVAC service technician for repair
2. Defective low
pressure switch not
shutting compressor o
when pressure drops
• Compressor would continue to run when thermostat is
satised and shuts blower and solenoid o. When space
warms up to set point, blower starts and the system
runs normally.
• Prolonged running without refrigerant ow will
damage or destroy compressor. If this condition exists,
call a CERTIFIED HVAC service technician.
Compressor short cycles, which is dierent from running intermittently
1. System pressure
controls defective.
Call a CERTIFIED HVAC service technician to verify and
repair.
2. System low on
refrigerant.
Observe for ashing in refrigerant sight glass located in 1/4”
copper tube at condensing unit. If ashing with bubbles,
call a CERTIFIED HVAC service technician for leak location,
repair, and adding refrigerant.
3. Condenser fan motor
defective
• Fan does not run with compressor.
• ¼” Copper tube at sight glass – very hot, compressor
very hot, runs short time, shuts o.
• Shut power o to condensing unit
• Call a CERTIFIED HVAC service technician for repair.
4. Compressor starting
components defective.
• Compressor very hot and hums when trying to start.
• Shut power o to condensing unit.
• Call a CERTIFIED HVAC service technician.
Evaporator coil freezes
1. Air lter, if equipped,
dirty
Clean or replace lter
2. Evaporator coil and/
or blower dirty
Clean coil and blower
3. Thermostat set point
too low.
Set point should not be lower than 50°. If so, increase to
above 50°
4. System low on
refrigerant
Check refrigerant “sight glass” in 1/4” tubing. Check for bubbles
after system has run for several minutes. If bubbles present,
call a CERTIFIED HVAC service technican. If sight is clear of
bubbles, refrigerant level is OK.
