How to fix eWelink thermostat error code “E2”?

I recently purchased Splenssyy eWelink-compatible smart thermostat.

The thermostat looks like it’s working, and its temperature readings show properly – but where it should read “heating”, it just says “E2”.

What do?


Status (or error code) “E2” means “External sensor needed”. So either your external sensor (NTC thermistor) is not installed or it doesn’t connect properly.

Note, that this should only be required for the “GB” -version, e.g. the electric floor heating thermostat that can supply up to 16 amps.


Things to verify to make sure your external temperature sensor is working properly.

Time needed: 10 minutes.

How to fix error “E2” with your eWelink thermostat?

  1. Restart your thermostat

    The easy first step is usually to restart the device – you should know which fuse to disconnect (as you should’ve disconnected it for setting the thermostat up in the first place), so start by doing that.

  2. Make sure you have external sensor installed

    I know, I know – GB version’s manual says the external sensor is optional.

    It is not.

    Go ahead and install it. Wiring diagram shows you how!

  3. Tighten the screws for the sensor

    Oh, you installed it already but still have the E2 error?

    Well – most likely one of the wires doesn’t connect properly. Tighten the screws a bit and you might be good.

  4. Adjust the wire to make sure it connects

    Maybe the connectors are broken – happened to one of my (many) thermostats!

    Strip a longer part of the wire, and double-fold it. Then reinsert it.


This eWelink-compatible thermostat is functional, but doesn’t exactly astonish with quality.

If you want to buy original Sonoff-products, you can get them from Itead’s online store, and if you use coupon code A0NESONOFF, you’ll get 10% off everything!

And if you want to follow my other Smart Home Adventures, head out to my other website 🙂

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