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heating does not turn off defective relays or software problem ?


I have my Tado thermostat for a bit over 2 years now, and the heating does not turn off anymore.

The central heating system is connected on the common and normally open connectors of the thermostat.

When I set the temperature to minimum, or off, the heating system keeps on going.

I don't hear the relays clicking when I change the temperature settings between off - minimum and maximum temperature, and when I measure the resistance between the common and normally open pins, it is always closed, and this is also the reason why the heating does not switch off anymore.

So I suspect either a defective relays, or a software problem, where the software does not drive the relays on or off anymore.

When i connect the wires of the heating manually, to switch it on, the current is 0.4A, and when I disconnect the wires, the voltage is 230V AC, so this is well within the specifications of the thermostat, and should not damage the relays contacts I suppose ?

I am starting to doubt the Tado build quality, as when I ordered it, I immediately had to return it because of a bad soldering of the pins that connect to the screw connector, on the printed circuit board of the thermostat, and now, a few months after warranty expired, there seems again to be a hardware problem.

My previous thermostat, which is also equipped with a relays, and is over 30 years old is still working fine and driving the heating system in the house of my daughter, whereas the new Tado thermostat already had 2 defects now.


  • Hi,

    I have got the same issue which started yesterday. I have installed additional two thermostats and that 'triggered' the problem. The old thermostat that is for more than a year started having this issue while the new Thermostat works fine.

  • Hi,

    I was able to repair my thermostat.

    There were 2 problems, some of the settings had changed, so the configuration that makes it drive the relays changed into something else, and I also found a bad soldering contact on the relays that is soldered on the printed circuit board.

    To solve the problem with the lost settings, I took out the batteries for 24h and re-configured it from scratch. Try this, if there is no further hardware problem it may solve your problem

    For me this still did not solve the problem, so I desoldered the relays, and tested it. the relays was ok, so I soldered it back onto the circuit board, and then everything worked again. So soldering the relays back on the board solved the bad soldering contact that revealed itself only after a bit more than 2 years.

    As an electronics engineer, I have the equipment for soldering and testing components, this needs to be done very carefull, otherwise it will damage the printed circuit board, so it is perhaps best not to try this yourself if you don't have electronics/soldering experience.

  • I have tried the battery removal and it did not help. Even though I am tinkering with electronics as a hobby, soldering is the least loved part of that, thus I did not go there :) Instead I have contacted Tado support and they hinted me to the solution. The problem was in the room/zone configuration. As I have mentioned, in my case the problem has been 'triggered' upon installation of additional thermostats and creation of additional rooms. Accidentally (or due to my absent mindedness, not sure yet) one of the new rooms got the existing thermostat assigned as controller for the room. As a consequence, the thermostat tried to heat both rooms to reach the set target temperature and it meant that the 'original' room got overheated because the thermostat wouldn't stop when the target temperature has been reached. The newly installed thermostat was radiator thermostat and the new room could have been configured by tado software to have the existing Smart Thermostat as controller or it could have been my own mistake. Nevertheless, now I am sure the thermostats are not faulty and everything works just fine.

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