Refrigerator Not Cooling - Diagnostic Tree

Symptom

Customer reports the refrigerator is running (compressor + interior light operating) but isn't keeping food cold. Freezer may or may not be working. Most common appliance call by volume; correct diagnosis on first visit prevents the "they came twice and still didn't fix it" review damage.

Likely Causes

In order of frequency for residential refrigerators in service:

• Condenser coils blocked with dust - 25 % of "not cooling" calls
• Failed evaporator fan motor - 15 %
• Failed defrost system (heater, thermostat, or timer) - 12 %
• Frost-blocked evaporator coil - 10 %
• Door seal failure (warm air leaking in) - 10 %
• Failed condenser fan motor - 8 %
• Refrigerant leak - 5 %
• Failed compressor - 5 %
• Failed control board / inverter - 5 %
• Other (low charge, capillary blockage, etc.) - 5 %

Diagnostic Steps

1. Listen. Open the door and listen. Compressor humming + interior fan blowing = system is "running." Compressor running but no fan = fan failure. Silence = power or control issue.
2. Check temperatures with a probe thermometer. Standard refrigerator: 37 - 40 °F. Freezer: 0 - 5 °F. Note BOTH compartments - a freezer that's cold but a fridge that's warm tells you the evaporator fan or damper is the issue.
3. Inspect the condenser coils. Behind or under the unit. Dust + pet hair = insulator; coils can't reject heat = warm refrigerator. Photograph the dust before cleaning; it's a powerful customer-education tool.
4. Pull the unit out + clean coils. Vacuum + brush. This alone fixes 25 % of service calls. Run the unit for 4 hours and re-check temps before further work.
5. If still not cooling after coil clean: inspect the evaporator coil (inside the freezer compartment, behind the back panel). Pull the panel.

• Heavy frost across the coil: defrost system failure. Check defrost heater continuity, defrost thermostat (open-at-temperature), and timer or board operation.
• Clean coil, no airflow: failed evaporator fan motor. Confirm with a voltage check at the motor.
• Clean coil, airflow OK, still warm: low refrigerant charge OR sealed-system issue. Most modern fridges aren't worth resealing; quote a replacement.

1. Check door seals. Close a dollar bill in the door at multiple points around the seal. If you can pull it out with no resistance, the seal is failed. Replacement is straightforward.
2. Check fan operation. Both condenser and evaporator fans should run when the compressor is running. A dead fan in either position causes warm-fridge symptoms.

Resolution

• Coils dusty: clean, monitor 4 hours, document temperatures returned to spec
• Evap fan motor failed: order OEM replacement; same-day repair if in stock
• Defrost system: identify the failed component (heater, thermostat, board) and replace
• Door seals: replace; clean the magnet contact area

Prevention

• Coil cleaning every 12 months on every customer (pet households: every 6 months)
• Door seal inspection at the same visit
• Customer education on not blocking the rear ventilation gap

References

• EPA Section 608 refrigerant handling regulations
• Manufacturer service literature for the specific make/model