Back to List of FAQs Q Why does my thermostat every now and then change settings by itself? A If your electronic thermostat randomly resets back to its original settings and time, it may be caused by radio frequency interference (RFI) or RF noise. This can occur from many sources but is more prevalent in gas furnaces with spark igniters. If this occurs, the RFI can be reduced and/or eliminated by adding an RF choke on the leads going from the furnace to the thermostat. This is very easy to do: The Radio Shack ferrite data line filter cat # 273-105 is a clip on device the goes around all the wires going to the thermostat. It is best to put it at the furnace end if easy to get to, but may also be used on the wires at the thermostat end. In some cases, one at each end is even better. If the wires are too large for that filter, the Radio Shack snap on RF choke cat #273-104 may be used.