E02
Sime
Safety Thermostat / Overheat Lockout
Furnace displays E02 and shuts down; often linked to overheat or safety thermostat activation.
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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 system circulation, Failed circulation pump, Dirty heat exchanger, Faulty safety thermostat
How to Fix / Troubleshooting
Safety first: Allow the furnace to cool fully. Do not bypass any safety devices.
- Check system circulation: Ensure valves on the flow and return lines are open and that radiators or zones are not all closed.
- Verify pump operation: Listen and feel for vibration at the Sime circulation pump when there is a heat demand. If silent, check the electrical connector and fuse.
- Reset safety thermostat: Locate the manual reset button on the overheat thermostat (usually on the heat exchanger). Press gently once the unit is cool.
- If E02 recurs: The underlying cause (pump failure, blockage, or scaled heat exchanger) must be corrected by a technician.
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Repair Difficulty
Hard
4/5
Required Part
Safety / Overheat Thermostat
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