How to Fix / Troubleshooting

Safety first: Isolate power before opening the thermostat or sensor back box.

Steps:

Inspect the remote sensor back box and cable route for screws or nails penetrating the cable.
At the thermostat, remove the remote sensor wires and measure resistance across them with a multimeter. A reading near 0 Ω indicates a short.
If the short is local to the sensor head, replace the Heatmiser remote air sensor.
If the cable is shorted in the wall, consider re-routing a new cable or switching to internal sensor mode if acceptable.
After repair, confirm the resistance is in the expected kΩ range and clear the E06 code by cycling power.

Thermostat shows E06 and temperature reading is unstable or locked

Possible Causes