E4
Tosot
High Discharge Temperature Protection / Compressor Discharge Overheat
Unit stops and displays E4, often during heating mode on heat pump models
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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
Blocked or dirty outdoor condenser coil, Low refrigerant charge causing superheat, Faulty discharge temperature sensor (T3), Poor airflow across indoor coil (clogged filter or blower issue)
How to Fix / Troubleshooting
Safety first: Turn off power to both indoor and outdoor units before cleaning or inspecting.
- Clean indoor filters and coils: Ensure indoor filters are clean and the evaporator coil is not blocked by dust or ice.
- Clean outdoor coil: Remove debris around the outdoor unit and gently wash the coil fins with water. Maintain at least 2–3 feet of clearance around the unit.
- Check discharge sensor: On the outdoor unit, locate the discharge temperature sensor clipped to the compressor discharge line. Make sure it is firmly attached and not damaged. Replace if the wiring is brittle or the sensor is cracked.
- Check fan operation: Confirm the outdoor fan runs at proper speed. A slow or non-running fan will cause high discharge temperature.
- If E4 returns: A technician should check refrigerant charge and system pressures. Persistent E4 may indicate a refrigerant issue or internal compressor problem.
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Repair Difficulty
Hard
4/5
Required Part
Compressor Discharge Temperature Sensor (T3)
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