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I have a problem with the thermostat of my furnace. This problem is wired but I'll try to explain it as clearly as possible.
When I turn the button of the thermostat, some temperatures can't be selected (they can never be), and sometimes, a temperature that can't be select appears briefly when I turn the button but disappears nearly immediately (and then the screen displays an other temperature).
Have you got any idea of how to fix this ?

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Can you supply the model of the thermostat or a picture? – bib May 9 '14 at 11:31
@bib It's a Scholtēs ! – Trevör Anne Denise May 9 '14 at 11:33
What temperatures can't be selected? – Tester101 May 9 '14 at 11:58
up vote 1 down vote accepted

From the description of the problem it seems like the thermostat is a digital type with a display that shows the temperature selection and then uses a rotary selector knob to allow setting the desired temperature.

The inability to zero into a particular temperature setting is probably caused by a damaged or faulty rotary selector knob. This type of selector is often times a switch with two connections into microcontroller on the thermostat electronics board. As the switch turns the two connections to the microcontroller at switched on and off in a pattern that allows the software of the microcontroller to detect the switch turning and what direction it is being turned. If the switch is broken, has dirt in it, or has a bad connection on the circuit board the microcontroller may mistakenly see many more or less "steps" of the switch pattern and thus not react in a way that allows you to set the selection that you desire.

In most cases the fix for this is to replace the thermostat with a new one. Only someone that has access to the proper testing equipment and spare parts is likely to be able to repair this type of problem.

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I'll bring it to the manufacturer then... thank you ! – Trevör Anne Denise May 9 '14 at 12:09

The rotary encoder or the button that the knob pushes as it turns is broken. Unless you're the kind of person that likes opening small electronics and replacing components, there's probably no way to fix this. Just buy a new one, or send it back to the manufacturer for repair/replacement.

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Thank you for your answer ! – Trevör Anne Denise May 9 '14 at 12:09

If this is the electronics board for your thermostat then the rotary selector switch in question is most likely the one shown marked below:

enter image description here

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