I have seven thermostats (for a fan coil central AC system) that unfortunately havd a big problem. When the relays (three big rectangles in black) are closed to turn on the fan they get quite hot.
The temperature sensor on the PCB picks up this heat and always reports the same room temperature which translates into the thermostat never switching off the fans. I have tried pulling the screen part of device (where the temperature sensor is) and leaving it hanging and it starts reporting accurate temperatures. The relays are warm to the touch.
I first looked at finding a way of cooling the relays so that they wouldn't warm up the temperature sensor but since they are so close together and this is placed inside the wall in a very small space nothing I tried worked.
I am now thinking of putting the temperature sensor with a wire further away from the relays so it doesn't warm up when they are closed but I am having trouble identifying it on the PCB.
I have searched similar topics and I think it can either be the a thermocouple (D2) in the picture or an SMD resistor. How can I accurately identify it so I can desolder it?
edit: I managed to desolder that component on the bottom and pull it away from the heat source, it is indeed the temperature sensor. Tks for the help
