HVAC room sensor

[jerichorick]

Yesterday I thought I saw a lump in the wall next to the bed. It was just the light playing tricks. But, what I did find is a warm spot on the wall under the light and fan switches! Wow! What's this all about?
I pushed the door trim out a bit and pried a small area open in the wall panel to gain access to the warm area. To my surprise I found a ceramic resistor in the wire raceway for the fan/lights and room temperature sensor.
The ceiling fan had been on low speed. This resistor is the low speed control. It should get warm. It just happened to be against the panel back so I could feel this area warmth.
Over the years I always had a problem with the room temperature accuracy for this zone, zone 2. Now I know why.

Heat rises. The two strips of wood that run up the wall to form the support for mounting the switches and containing the wires acts like a chimney. Being that the sensor is above the resistor, it responds to this false input and reports this to the thermostat. If the heat pump or A/C is on along with the fan I will not get good heat or cooling control.
DW needs me to close. Hope this peaks your interest.
Rick Y