Danfoss E29

What does Danfoss E29 mean?

On the Danfoss ERC 21X refrigeration controller, E29 means the Sair (air temperature) sensor is defective or its electrical connection is lost. The controller cannot read cabinet air temperature, so it cannot regulate cooling normally. In an alarm situation the display alternates between the actual air temperature and the active alarm codes, and the alarm relay is activated.

Symptoms

• Display alternates between the air temperature and the code E29.
• Cabinet air temperature reading is missing or shows a fault value.
• Temperature regulation becomes unreliable.
• Alarm relay is activated.

Common causes

• Air temperature sensor is defective.
• Electrical connection to the air sensor is lost or broken.
• Loose or corroded terminal at the sensor input.
• Sensor cable damaged or pinched.

Diagnostic steps

1. 01

   Read the alarm code

   Observe the display alternating between air temperature and E29 to confirm the air sensor is the source of the alarm.

2. 02

   Inspect the air sensor wiring

   Power down and check the air sensor cable and terminals for breaks, looseness, or corrosion; re-seat the connection.

3. 03

   Measure the air sensor

   Disconnect the sensor and measure its resistance against the type fitted (NTC 5 kΩ, NTC 10 kΩ, PTC 990 Ω, or Pt1000); an open or shorted reading confirms a failed sensor.

4. 04

   Replace the air sensor

   Fit a new sensor of the correct type, route the cable away from power wiring, and confirm E29 clears on power-up.

When to call a professional

If the air sensor cannot be reached easily, or replacing it does not clear E29, a refrigeration technician should confirm the correct sensor type and check the controller input. Using the wrong sensor type causes incorrect readings and poor temperature control of stored product. Trained staff can also verify the wider wiring and controller configuration when a sensor fault recurs, protecting both the equipment and the goods inside.