Indoor unit displays E4 and shuts down during heating mode
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.
Possible Causes
How to Fix / Troubleshooting
Safety first: Turn off power at the outdoor disconnect before touching the outdoor unit. Beware of sharp coil fins and moving fan blades.
Steps to try:
- Inspect outdoor coil: In heating mode, some frost is normal, but a solid block of ice is not. If the coil is completely iced over, turn the system OFF and allow it to thaw naturally.
- Check outdoor fan: With power restored and unit in HEAT, verify the outdoor fan runs. If the compressor runs but the fan does not, suspect the fan motor or capacitor.
- Clean coil: After thawing, gently rinse the outdoor coil with water to remove dirt that can interfere with defrost sensing.
- Check coil sensor connection: If accessible, locate the outdoor coil temperature sensor clipped to the coil and ensure its plug is firmly seated on the outdoor PCB.
When to call a pro: If E4 persists, the outdoor coil sensor or outdoor main PCB may need replacement and defrost parameters checked.
Repair Difficulty
Required Part
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