E04
Baxi Outdoor Coil Temperature Sensor Fault

Outdoor unit does not start; indoor unit shows E04 and cooling/heating is unavailable

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Safety Warning

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

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Possible Causes

Failed outdoor coil NTC sensor, Sensor not fixed to coil, Corroded sensor connector, Faulty outdoor main PCB

How to Fix / Troubleshooting

Safety: Isolate power at the outdoor isolator. Outdoor units contain high voltage and moving parts.

Steps:

  • 1. Remove outdoor cover: After power is off, remove the service panel to access the PCB and sensors.
  • 2. Locate coil sensor: The outdoor coil NTC is usually clipped to the condenser coil tubing or fins with a plastic clip.
  • 3. Check mounting: Ensure the sensor is firmly attached to the coil and not dangling or displaced.
  • 4. Inspect wiring: Follow the sensor cable back to the outdoor PCB. Look for damage, rodent bites, or corrosion at the connector. Clean and reseat the connector.
  • 5. Test and replace: Measure resistance; if open or shorted, replace with a Baxi-compatible outdoor coil NTC sensor.

Note: If the sensor tests good but E04 persists, the outdoor PCB sensor input may be defective and requires professional replacement.

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Repair Difficulty

Hard 4/5

Required Part

Outdoor Coil Temperature Sensor (NTC)
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