Why Your Refrigerator Compressor Makes a Clicking Noise and Refuses to Start
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You head into your kitchen to get a glass of water, and you realize that your refrigerator is totally silent. Then you hear it; a small hum, followed by a loud, sharp click of what sounds like metal on metal. Three minutes later, that same hum and click repeats again.
When you open your freezer, your ice cream is already beginning to melt.
That click click click sound is the universal distress signal of a dead refrigerator. Most people assume that the entire appliance is not repairable and will start looking for a brand new one, but in fact 80% of the time your compressor motor will actually be fine, the problem just lies with one small and cheap electrical part on its side.
Below is a detailed electrical and mechanical explanation of exactly why your refrigerator is clicking, what is actually not starting, and how to accurately diagnose it:
1. What is that "click" actually (Overload Protector)?
This clicking is NOT coming from the motor. This click is coming from the Overload Protector (OLP), which is a safety device.
A compressor needs a large surge of power in order to turn. If for some reason the motor can't start spinning, the electric current that it's pulling can be up to ten times what it should be. The OLP will detect the excessive current and its small bimetallic disc inside, which will heat up from the overload, will bend itself until it pushes against the circuit contacts and snaps them open. You can hear that "snap". A few minutes later the disc will cool, and will snap back into position and the cycle will repeat, you will hear the hum and then the click again.
2. What is actually not starting (PTC Start Relay)?
Since your OLP is doing its job and is clicking off to prevent damage, you are asking why the motor can't actually start in the first place! This will almost always be caused by the failure of a PTC (Positive Temperature Coefficient) Start Relay.
Your compressor motor has a main run winding and a start winding. The PTC start relay is responsible for sending a brief shot of high voltage to the start winding, so that it gives the motor an initial kickstart. Inside of the PTC relay is a small ceramic disc. When electricity passes through it, it becomes extremely hot, and its resistance increases dramatically; in effect shutting off the start winding once the motor has started.
Over many uses and heating and cooling cycles. the small fragile ceramic disc inside the PTC is most likely to break. When the PTC is broken, zero electricity reaches the start winding and the motor hums, but cannot overcome the internal load it encounters upon startup and begins to overheat and eventually trigger the OLP.
The Diagnostic Test: Unplug the refrigerator, pull the small plastic cover off the side of the compressor, and shake the component around inside it. If it rattles like a baby toy it is broken.
3. Dead Start Capacitor:
In addition to a PTC relay, many heavy-duty compressors have a start capacitor. Think of this like a huge high-voltage battery that is hooked up to the start winding when the motor is trying to start up. If the start capacitor bulges, leaks fluid, or simply no longer holds a charge, your motor cannot overcome the mechanical load it's placed under and begins to pull excessive current to trigger the OLP.
4. Head Pressure Issues:
Your compressor will click off if there is a physical problem and if you can rule out electrical issues then this is a likely candidate. Condenser coils are responsible for dissipating the heat that is drawn out from the inside of your refrigerator. If they are clogged with enough dirt, pet hair, and lint, it becomes too difficult for them to get rid of the heat, and your head pressures climb drastically. The motor is unable to turn against the high pressure.
NOTE: Always unplug the appliance before performing any diagnostics or repairs.
The Fix: Unplug it, pull the unit away from the wall and vacuum the condenser coils, then vacuum them again!
5. A seized motor:
If none of the previous potential causes worked and you replaced the start relay, tested the start capacitor, and cleaned the condenser coils, you likely have a dead compressor. This means the internal components of the motor are stuck together due to lubrication failure. It cannot physically turn no matter what. The solution is to have the compressor replaced by an HVAC technician, but it may very well cost more than the entire refrigerator at this point.
If your refrigerator is clicking off and not getting cold, pull it away from the wall, put your ear next to the compressor motor, and see if the start relay is making noise inside it.