You depend on your AC to get through summer, so the last thing you want is to realize your AC unit isn’t working. Don’t call a technician just yet.
Testing Your HVAC Thermostat
There are a few steps you can take to determine whether the thermostat is the issue or if your air conditioning system is the problem. After all, there’s no reason to make a call if a fresh battery is all you need to kick the AC unit into high gear.
First, make sure the thermostat switch is in the “on” position and set to “cool” or AC. If that doesn’t solve the problem, check a programmable thermostat for any override programs that may have engaged and caused an issue with the air conditioner.
In some cases, programmable thermostats require batteries. If so, replace them with new batteries to make sure the thermostat has power as this might solve the problem.
Have a family member or a friend stand by the furnace while you stand by the thermostat. Use your cell phone or, if you have them, walkie-talkies to communicate while running this test. Once everyone is ready, change the thermostat switch to heat. The furnace should respond immediately, but the AC might have a delayed response.
In this next step, you should slowly raise the thermostat setting until you hear a click. Be sure to inform your helper to know what you are doing. Your helper should hear the furnace make a sound, indicating that the furnace received the signal to start. If not, the thermostat is likely the problem and needs to be replaced.
The next thing you should do is turn off the furnace breaker and pull the cover off the thermostat to reveal the wires. As thermostats use a 24-volt low-voltage transformer, there is no risk of electrical shock. That said, it’s a good idea to shut the power down to the unit.
The next thing you should do is take a picture of the thermostat’s wire connection with a digital camera or cell phone. This ensures you know exactly how to properly reconnect everything. Then, locate and loosen the terminal screws labeled “R” or “RH” and “W.”
Once the terminals are loose, remove the wires and twist the ends together. This step bypasses the thermostat. After telling your helper to listen to the furnace, turn the furnace breaker back on. If the furnace responds, the thermostat is bad.
At this point, you should contact to set up an appointment with a comfort specialist to have the thermostat replaced.