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REFRIGERATION

Troubleshooting

Temperature fluctuating up and down

Cabinet air temperature always moves. The compressor runs until the air reaches the cut-out point, stops, and the air warms until the cut-in point. Defrost adds a short, larger rise, and every door opening sends a spike. Food, with its thermal mass, changes much more slowly than air, so a display jumping a few degrees does not always mean food is at risk. The concern is when product temperature itself drifts above 5 °C in a refrigerator or above −18 °C in a freezer, or when swings are getting wider over time. Measure first, then decide whether you are looking at normal cycling or a fault.

First, check these

  1. Put a probe thermometer in a glass of water or a food simulant on a middle shelf. Compare its slow-moving reading with the display's air reading.
  2. Note when swings happen: at service peaks, after deliveries, at regular intervals (defrost), or at random.
  3. Check whether a defrost icon shows during the warm spikes.
  4. Check door closing, gasket condition and how often the door is opened during service.
  5. Note any power cuts or voltage dips; some controllers restart with a delay after an outage.

Likely causes

  1. 1. Door openings during service

    You can check this

    Signs: Spikes line up with busy times; air temperature recovers quickly once the door stays shut.

    Fix: Organise stock to shorten openings, keep frequently used items at the front, and consider an undercounter unit at the line so the main reach-in is opened less.

  2. 2. Defrost cycles

    You can check this

    Signs: Regular warm periods at set intervals, display may show a defrost icon or the last reading.

    Fix: This is normal. If food temperatures stay in range, no action is needed. If defrost seems too long or frequent, ask a technician to review the settings.

  3. 3. Loading warm product

    You can check this

    Signs: Cabinet takes hours to recover after loading cooked food or a big delivery.

    Fix: Cool cooked food first using shallow trays or a blast chiller, and stagger deliveries into the cabinet.

  4. 4. Power cuts or voltage sags

    Technician job

    Signs: Swings coincide with outages or stabiliser switching; controller restarts or shows a power-loss alarm.

    Fix: Use a voltage protector or stabiliser with a time delay and keep a log of outages. An electrician can check the supply.

  5. 5. Controller differential set too wide

    Technician job

    Signs: Long gaps between compressor starts, air swinging well beyond what the product needs.

    Fix: A technician can adjust the differential and check the setpoint. Do not change hidden parameters without the manual.

  6. 6. Sensor fault or poor sensor position

    Technician job

    Signs: Display jumps erratically or reads very differently from your thermometer.

    Fix: A technician should check probe position, wiring and condition and replace if faulty.

When to call a technician

Call a technician if food temperatures go out of range, if swings are growing over weeks, if the display behaves erratically, or if the cabinet does not recover after the door stays closed. Share your two or three days of thermometer log and the times of door openings and power cuts; it shows the technician which cause to chase.

Isolate power before moving any sensor or opening a cover. Controllers and sensors connect to mains-voltage circuits, and the sealed system on hydrocarbon (R290 or R600a) units must only be opened by trained technicians.

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