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REFRIGERATION

Troubleshooting

Temperature display reading wrong

The display on a commercial refrigerator usually shows the air temperature at one sensor, often in the return air path or near the evaporator. Your food may be at a different temperature, and air at the top shelf may differ from the bottom. So a mismatch between display and thermometer is not automatically a fault. It is a fault when the difference is large, inconsistent, or getting worse, because then the controller is making decisions on bad information. For food safety logs, a reliable reading matters more than a pretty display.

First, check these

  1. Check your own thermometer first. An ice-slurry test (crushed ice with a little cold water, stirred, probe in for a minute) should read close to 0 °C.
  2. Place the checked probe in a glass of water near the cabinet sensor, wait an hour with the door closed, and compare with the display.
  3. Repeat at the top and bottom shelves to see the temperature spread inside the cabinet.
  4. Check whether the display is showing a different value from the cabinet air, such as setpoint or evaporator temperature, after someone pressed a button.
  5. Make sure you are not comparing during or just after a defrost, a delivery or a long door opening. Readings need time to settle before they mean anything.

Likely causes

  1. 1. Comparing air with product temperature

    You can check this

    Signs: Display swings while your probe in water moves slowly; average values roughly agree.

    Fix: This is normal. Log product or simulant temperatures for food safety and use the display as a guide.

  2. 2. Display set to show another sensor or value

    You can check this

    Signs: Display matches the setpoint exactly or reads very cold, as an evaporator probe would.

    Fix: Check the manual for how to return the display to cabinet temperature.

  3. 3. Sensor moved out of position

    Technician job

    Signs: Probe clip loose, probe lying against the coil or in the direct air outlet, or buried in stock.

    Fix: Keep stock away from the sensor area. A technician should refit a probe that has come loose.

  4. 4. Calibration offset needed or changed

    Technician job

    Signs: Steady, consistent difference of a degree or more against a checked thermometer.

    Fix: Many controllers allow an offset. A technician should set it after a proper comparison.

  5. 5. Damaged probe or connection

    Technician job

    Signs: Erratic jumps, readings frozen, or an error code for the probe; cable crushed in the door or wet connector.

    Fix: A technician should replace the probe and protect the cable route. Moisture in connectors is common in monsoon months.

  6. 6. Controller or display damaged by a voltage spike

    Technician job

    Signs: Display shows nonsense characters, dims, freezes on one value, or the problem began right after a power surge or lightning storm.

    Fix: Isolate power, wait a few minutes and restart once. If the fault remains, a technician should test and replace the controller; do not keep power-cycling it.

When to call a technician

Call a technician if the display and a checked thermometer differ consistently by more than a degree or two, if readings jump erratically, or if a probe error appears. Until then, rely on your checked thermometer for food-safety records and note the difference in your log. Bring your thermometer readings and shelf positions to the visit.

Isolate power before moving anything near the sensor or removing covers. Controller wiring runs at mains voltage. Leave refrigerant work on hydrocarbon (R290 or R600a) units to trained technicians.

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