Thermostat shows E8 and the display may flicker or freeze
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: Turn off power at the breaker before removing the thermostat from the wall. Use a non-contact tester to confirm power is off.
Steps to troubleshoot E8 (memory error):
- 1. Power cycle: Turn the breaker OFF for 2–3 minutes, then ON. Observe whether E8 reappears after boot.
- 2. Factory reset: Using the thermostat's front panel controls, perform a factory reset (see Stelpro manual for the exact button sequence). This clears corrupted settings stored in memory.
- 3. Reconfigure settings: After reset, re-enter your schedules, setpoints, and Wi-Fi credentials. Monitor operation for several days.
- 4. Protect from surges: Install a whole-home surge protector or a dedicated surge device for the heating circuit to prevent future memory damage from line spikes.
- 5. Firmware reflash (if available): Some Stelpro models allow firmware reinstallation via the app. If offered, follow the instructions carefully and ensure power and Wi-Fi remain stable during the process.
- 6. Replace thermostat: If E8 persists after factory reset and firmware update, the EEPROM or flash memory on the main board is likely defective. Replace the thermostat.
Warning: Do not repeatedly power-cycle the unit rapidly; this can worsen memory corruption.
Repair Difficulty
Required Part
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