Compressor Not Running in Fridge? Reasons Explained

Is your refrigerator not cooling properly even though the lights are on? You open the fridge door and don't hear the usual hum of the compressor? If so, your fridge compressor not running could be the culprit.

The compressor is the heart of a refrigerator's cooling system. It circulates refrigerant through the sealed system to absorb heat from inside the fridge and release it outside. When the compressor stops running, it means no refrigerant flow and no cooling.

Common Causes of a Fridge Compressor Not Starting Up

There are several possible reasons why your fridge compressor won't kick on:

• Failed start relay - This relay provides the initial power surge to start the compressor. If it's burned out, the compressor won't start.
• Faulty start capacitor - The capacitor provides extra torque to start the compressor motor. A bad capacitor can prevent starting.
• Compressor overload tripped - The overload protector shuts off power if the compressor overheats. You'll need to reset it.
• Seized compressor - If the internal parts are frozen or locked up, the compressor may not start at all.
• Open motor windings - Bad connections or broken wires in the compressor windings prevent starting.
• Low refrigerant level - Not enough refrigerant can lead to compressor overheating or malfunction.
• Faulty main control board - The control board provides power to compressor components. If it's defective, the compressor won't start.

Checking Compressor Start Relay and Capacitor

The start relay and capacitor provide the initial jolt of power to get the compressor motor spinning. If either component is bad, the compressor just clicks or buzzes but doesn't start up.

Check for signs of overheating on the relay or capacitor. Remove the wires and test capacitor microfarads with a multi-meter. A capacitor reading out of spec indicates failure. Replace the start relay and capacitor as a set if faulty.

Resetting a Tripped Overload Protector

Compressors have an internal overload protector that cuts power if they overheat from a fault or cut-in/cut-out too frequently. You'll need a multi-meter to test continuity on the overload.

Reset the overload by switching power off for at least 30 minutes. This gives the protector time to cool and reset. If it trips again, have a technician diagnose the cause - could be low refrigerant, bad relay, or failing compressor.

Fixing Low Refrigerant Issues

Not having enough refrigerant can prevent the compressor from starting. Low refrigerant causes inefficiency and overheating. Adding refrigerant requires piercing the sealed system, so a professional should handle it.

Signs of low refrigerant:

• Frost buildup on evaporator coils
• Unit runs constantly but inadequately cools
• High operating pressures

Refrigerant leaks are often caused by a failed evaporator, condenser, or lines punctured during repairs. Detect leaks early before compressor damage occurs.

Getting Power to a Non-Running Fridge Compressor

If the compressor isn't starting, first check that it's getting power:

• Verify outlet voltage and breaker/fuse - Use a multi-meter to check 120V from wall and to compressor.
• Inspect terminals and tighten connections - Loose wires at the compressor can prevent power transfer.
• Check compressor windings for open circuit - Use a multi-meter to test winding resistances. A winding issue means replacement.
• Test start components like capacitor and relay - Faulty start components leads to no power to compressor.
• Replace control board if diagnosed bad - The control board regulates power to sealed system.

Diagnosing Compressor Electrical Issues

Use a multi-meter to diagnose why power isn't getting to the compressor motor windings. Check the start relay, capacitor, and windings for electrical continuity issues:

• Start relay - Test contacts for open circuit. Replace relay if faulty.
• Start capacitor - Check microfarad values. Change out if reading is too high/low.
• Windings - Check winding resistances match spec values. An open winding requires compressor replacement.

Problems with windings or internally grounded windings require installing a new compressor. Avoid continuously resetting a tripped overload without diagnosing root cause.

Inspecting Fridge Control Board

The control board regulates sealed system components like the compressor, condenser fan, evaporator fan, and defrost heater. If the control board is bad, the compressor may not start up.

To test, disconnect all power and leads from the control board. Check continuity between terminals with a multi-meter. Compare to wiring diagram specs. If readings are off, replace the faulty control board.

Troubleshooting No Sound or Hum from the Compressor

If you don't hear the usual humming sound when the refrigerator is on, the compressor may not be running. Test start components and listen closely:

• Inspect start relay and capacitor - Faulty components prevent compressor operation.
• Feel for vibration - Place hand on compressor to feel if it's running.
• Listen for faint hum - Modern, inverter compressors run very quietly.
• Check windings for seized compressor - Bad windings lead to locked rotor.

Replace the start capacitor and relay if defective. If compressor windings test bad, the sealed system may be contaminated and require a new fridge.

Causes of a Noisy Fridge Compressor

Loud or abnormal sounds from the compressor indicate an underlying problem:

• Metallic knocking noise - Rods/valves inside compressor are damaged.
• High-pitched squealing - Bad or worn-out bearings inside compressor.
• Grinding noise - Debris in system or broken compressor parts.
• Chattering/rattling - Low refrigerant level or obstruction in system.

Have a technician inspect and diagnose odd compressor noises. Attempting repairs on a sealed system without expertise risks causing further damage.

Preventing Frequent Compressor Failure

You can minimize compressor breakdowns by:

• Regularly cleaning condenser coils - Dirty coils lead to overheating and failure.
• Replacing worn door gaskets - Helps maintain proper temperature and cooling cycles.
• Letting air circulate behind fridge - Improves heat dissipation and prevents overtaxing compressor.
• Avoiding voltage issues - Use surge protector. Voltage spikes damage compressor.
• Not overloading fridge capacity - Overstuffing strains compressor operation.

Proper refrigerator maintenance goes a long way in extending compressor lifespan. Diagnose and fix minor issues early before catastrophic failure occurs.

Maintaining Proper Defrost System Operation

Faulty defrost components lead to compressor overloading. Ensure:

• Defrost heater adequately melts frost on evaporator
• Defrost thermostat accurately terminates defrost cycle
• Defrost timer energizes heater element for proper duration

Continuous frost buildup prevents heat transfer. The compressor works harder, overheating and eventually failing. Test defrost components and replace if faulty.