Commercial Fridge Clicking But Not Cooling
Commercial Fridge Clicking But Not Cooling: Diagnosing Compressor Failures
In a high-pressure commercial kitchen, bar, or retail store, your upright fridges, prep counters, and bottle coolers work non-stop to protect perishable stock. One of the most common and distinct mechanical warning signs is an under-counter or upright fridge that suddenly stops cooling and starts making a repeated mechanical clicking sound.
The sound pattern is almost always identical: a distinct click, followed by a brief low hum for 2 to 5 seconds, then a louder click, followed by complete silence. A few minutes later, the cycle repeats.
If your fridge is doing this, the internal compressor motor is struggling to start and is tripping its safety switches. Here is what that noise means, why it happens, and the steps you must take immediately to prevent complete motor burnout.
Understanding the "Click": The Thermal Overload Switch
The clicking sound you hear is not coming from a thermostat or electronic display; it is the thermal overload protector engaging.
The compressor is the heart of your refrigeration system, pumping refrigerant through the sealed circuit. Because compressors require a massive surge of electrical current to start rotating against internal pressure, they rely on specialized starting components (a start relay and capacitor).
If the motor fails to turn over within 2 to 3 seconds:
Electrical current spikes dangerously high.
The internal motor windings heat up rapidly.
The bi-metallic overload switch clicks open to cut power and prevent the compressor from catching fire.
Once the switch cools down after several minutes, it resets, attempts to start the motor again, fails, and clicks off once more.
The 3 Most Common Causes
1. Faulty PTC Start Relay or Capacitor
In approximately 60% of clicking commercial fridges, the compressor itself is mechanically sound, but the external starting electrical components have failed.
PTC Start Relay: A small solid-state switch clipped to the side of the compressor that directs current to the start winding for split seconds during startup. Over time, internal ceramic discs crack or burn out from electrical arcing.
Run/Start Capacitor: Stores electrical energy to give the compressor the initial rotational torque it needs. If a capacitor bulges, leaks oil, or loses capacitance, the compressor cannot overcome internal head pressure and stalls out.
Replacing a faulty relay or capacitor is an inexpensive, fast repair that takes an engineer less than an hour.
2. Severely Blocked Condenser Coil (High Head Pressure)
Commercial kitchens are full of airborne cooking oils, flour dust, and grease. Upright fridges and prep counters pull ambient air across their bottom or top-mounted condenser coils to dump heat.
When these coils become matted with dirt and grease:
Heat cannot escape the refrigerant gas.
Head pressure inside the copper lines rises to extreme levels.
When the compressor attempts to start, the back-pressure is too immense for the motor to turn against.
The motor stalls, draws locked-rotor amperage (LRA), and trips the overload switch.
3. Mechanically Seized Compressor (Locked Rotor)
The worst-case scenario is an internally seized compressor motor. This occurs when:
The system has operated with a slow refrigerant leak, causing the compressor to run without sufficient oil return.
Overheating has carbonized the internal lubricating oil, causing the pistons or scrolls to physically weld together.
An internal bearing or valve plate has shattered.
If the rotor is mechanically locked, no amount of electrical assistance will spin it. The compressor must be decommissioned, recovered under F-Gas guidelines, and replaced.
What Kitchen Staff Should Do Immediately
Step 1: Turn Off the Power at the Isolator / Wall Plug
Do not leave a clicking fridge powered on.
Every time the overload switch attempts to start a stalled compressor, intense heat builds up within the internal motor copper windings. Cycling on the overload switch for hours will burn away the insulating varnish on the windings, turning what could have been a simple £80 relay replacement into a £1,000+ full compressor replacement. Turn off the socket immediately.
Step 2: Relocate High-Risk Perishables
Commercial upright fridges lose temperature rapidly once the compressor cuts out. Move all high-risk food items—including raw meats, dairy, cooked poultry, and prepped fish—into another walk-in or service fridge before the cabinet temperature rises above 8°C.
Step 3: Inspect the Condenser Filter
Look at the ventilation grille at the bottom or top of the fridge. If the black radiator fins behind the grille are choked with grey lint, grease, or dirt, vacuum the surface gently using a soft brush attachment. Never use wire brushes that bend the delicate aluminum fins.
Repair vs. Replacement: What to Expect from an Engineer
When an F-Gas registered engineer arrives, they will conduct systematic diagnostic testing:
Resistance & Megger Testing: Measuring the resistance between the Run, Start, and Common electrical pins on the compressor to check for open circuits or ground faults.
Capacitor & Relay Bench Test: Testing microfarad ratings and electrical continuity on the starting gear.
Current Draw (Amperage) Check: Checking if the unit draws acceptable running current or spikes to locked-rotor amperage.
If the compressor windings are intact and the starting relay is the culprit, your fridge can often be back up and running within a single service visit.
Fast Commercial Kitchen Breakdown Engineering
Do not let a failed prep counter or display fridge interrupt your service. R4NK1N carries diagnostic gear, replacement relays, commercial capacitors, and refrigerant recovery equipment to get catering equipment operational quickly.
Call R4NK1N on 0330 043 1804 for 24/7 commercial refrigeration repair and maintenance across the Midlands and nationwide.
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