While there are numerous components to an HVAC system, the thermostat is your source of control. When your thermostat is out of commission, you’ll eventually experience some uncomfortable conditions within your living space, and perhaps even increased energy bills.
The following are several common thermostat problems you might experience:
- Cooling comes on when you set the system to "Heat," or vice versa
- Both heating and cooling activate simultaneously
- Batteries die quickly
- Buttons are unresponsive
- Display has incorrect temperature and system doesn’t react
- Display goes blank
Your manual should cover most or all of these topics in the troubleshooting section, and, oftentimes, the solution is simple. However, if your furnace or AC won't start or stop after troubleshooting, a new thermostat might be necessary. An inaccurate temperature reading, even after a thorough cleaning and examination of the wires and terminals, is another sign you should replace the device.
Before buying a replacement thermostat, ensure that your system is compatible. For example, you will need to know the voltage of your system. The most common is 24V, but in some cases electric heaters require line-voltage thermostats instead. A voltmeter could come in handy here, but all of the system requirements should be listed in the packaging.
Where you place your thermostat in your living space can affect how well it works. Placing it in direct sunlight, near a window, or beside features such as an oven can lead to inaccurate readings. In addition, keep it away from furniture or other structures that can impede air flow. Of course, if the thermostat location was originally in an ideal spot, don’t bother relocating. The following process assumes you will be using the same spot.
Note that this process could vary based on your specific unit. When in doubt, ask a technician or consult the manual.
- Turn off the broken unit and turn off the HVAC system via the fuse box.
- Remove the cover, but leave the wires for the moment.
- Label the wires with the letters of the corresponding terminals. Take a picture or write notes to help you remember everything.
- Disconnect the wires and take off any remnants of the old wall plate.
- Mark the placement of the new holes and drill the holes, if necessary.
- Guide the wires through the new wall plate. Secure the plate in place.
- Connect the wires to the new thermostat’s terminals, using the labeling system you created as well as the product instructions. This is where the process will likely vary depending on the unit you bought.
- Secure the unit to its wall plate and insert the batteries.
- Turn on the power and follow the thermostat’s instructions to complete setup.
If the previous thermostat was an older model with mercury tubes, note that these need to be handled with care and disposed of properly.