How to Repair a Heat Controller for Comfort Air

A heat controller is a component of a heater or air conditioning system that regulates temperature to a desired comfort air, a condition where indoor conditions are considered comfortable by the occupants. It ensures that heat, cool and humidity are circulated in a controlled manner in your home. The controller can occasionally breakdown. Repairing it will depend on whether you are using mechanical or a digital one.

Things You'll Need

• Soft-bristled brush
• Batteries
• Neon tester
• Adhesive tape
• Level
• Pen
• Replacement thermostat/heat controller
• Screwdriver
• Wire cutter
• Wire stripper

Instructions

Digital Thermostat

1. Check the power switch and confirm whether the heat controller it is turned on. It may have been turned off by mistake causing it to stop functioning.

2. Establish whether the room temperature shown on your thermostat matches that on your temperature. Any difference will indicate your heat controller has a bad sensor. Replace the sensor.

3. Check the temperature of your system’s thermostat. Take two temperatures into consideration; the set point temperature (your desirable temperature) and the room temperature (your indoor temperature). Your heat controller should run if the set point is below the room temperature. Calibrate your room temperature. Bring both the set point and the room point to balance. Both temperatures need to be at level to work properly.

4. Inspect the thermostat wire connections. Remove the thermostat cover and check that the connections are in proper condition. R, W, Y, G and C are the typical heat controller connections. R represents 24 volt power, W is for heat, Y for cooling, G for fan and C the common side of 24 volts. Check whether there is a wire connection to C. If missing then the heat controller is powered by battery. Check that R connects to W, Y or G. Ensure that all wire connections are properly in place. If not, fix them to their proper place.

5. Check whether the back display light of the thermostat functions. If it does not, confirm whether the batteries are out of use and replace. Some thermostats use AA or AAA batteries for the back light.

Mechanical Thermostat

1. Inspect the circuit breakers on your heating or air conditioning system if the thermostat does not turn on. Turn them on if they are off. If they were already on, turn them off and then on again to reset.

2. Open the panel of the battery compartment and check whether the batteries are properly connected. Remove them and replace them with new batteries if they are old. Replace the panel.

3. Check whether your air conditioning or heating unit regulates temperature as per your requirements. If not, unscrew the screws on your thermostat cover. Remove the cover and clean the interior free of debris and dirt with a soft brush.

4. Check your thermostat wire connections. Confirm whether the wires are correctly fitted to their terminals. Replace the wires to their proper terminals. If in correct terminals, remove them and place them back to their terminal clamp.

5. Check that your thermostat is at level with the wall (if using a thermostat with a mercury switch). Use your thermostat’s cover to locate the calibration disc. Find the small lever arm (heat anticipator level arm) on the disc. Shift it one calibration point closer to the “Longer” setting if your heating unit goes on and off frequently. If it allows room temperature to rise higher or drop lower than it is supposed to before going off, move the lever one mark away.

References

• Technical Development Program: Introduction to HVAC: ABCCS of Comfort
• University of Hong Kong: Brief Notes on Air Conditioning System Design
• Lawrence Berkeley National Lab: How People Actually Use Thermostats