Thermostat shows incorrect temp

My thermostat was working fine until I went away on holiday and turned the power off for a month. I came home to the 45 degree heat and turned the power back on. Ever since it now shows about 3 degrees higher than it is. I have had to put a thermometer next to it to tell.

any ideas how I can fix this? I've tried turning the power off again now that it's much cooler but that hasn't worked?

 

Using toolkit on the Temperature page you can add an offset to calibrate the displayed temperature.

I have found all my thermostats read slightly high. I assume this is due to the internal heat generated by the unit. 3 degrees seems a bit much though.

 

thanks Ashly, I'll give that a try.

still i'm surprised it happened in the first place and that there is no way to reset it. Of course this makes me think it will happen again on my next long departure.