Some possible solutions include resetting the thermostat to factory settings, checking the circuit breaker, replacing the air filter, checking the outdoor unit, checking the indoor unit, replacing the thermostat's batteries, and checking the connections and wiring for any damage.
Check the Power Source: Ensure your thermostat is receiving power. Replace batteries if your model requires them or check the circuit breaker if it's hardwired. Inspect the Wiring: Over time, wiring can degrade. Inspect for any loose connections or signs of wear.
Checking basic thermostat settings, power supply components, and air filter conditions are essential to troubleshoot why an AC unit isn't turning on. More advanced issues requiring professional attention include faulty wiring, a malfunctioning outdoor unit, a bad capacitor, or incorrect thermostat calibration.
Honeywell thermostat not turning on? Usually, the first culprits of a failed Honeywell thermostat are the batteries. While today's modern batteries can last quite a few years, they will all eventually run out of power. In addition, a number of factors can cause them to fail prematurely.
Clogged air filters are one of the most common reasons a thermostat clicks but AC does not turn on. A filter cleans the air before it circulates throughout your home, trapping dirt particles, dust, and pollen. Over time, these contaminants will clog the filter, limiting airflow to the HVAC system or furnace.
The main reasons your AC unit outside is not turning on could be something that has tripped the circuit breaker, something is blocking the fan's airflow, or the condensing unit is damaged. Other potential issues could be the thermostat isn't set correctly or the compressor could be malfunctioning.
Check the configuration of the thermostat to make sure it is controlling the equipment properly. Verify that the thermostat is wired correctly. Make sure all of the wires are secure and in the correct terminals. Make sure the voltages are between 18 and 30 VAC or 20 and 30 VAC depending on the thermostat model.
Power Off the Thermostat: Turn off the thermostat's power source, usually by flipping the circuit breaker or removing the batteries. Press and Hold the Reset Button: With the power off, press and hold the Honeywell thermostat reset button for about 5-10 seconds.
A bad thermostat can be detected when your AC or furnace is not turning on, your HVAC systems are not turning off, the thermostat not responding, your HVAC system is short-cycling, the room temperature not matching the temperature displayed on the thermostat, and the programmed setting resetting themselves.
HVAC System Suddenly Quits Working
Try replacing the batteries, then check for a blown fuse or tripped breaker in the electrical panel. If the thermostat is still unresponsive, make sure the breaker is shut off and remove the cover.
Signs of a Faulty Thermostat
AC Refuses to Start or Stops Suddenly: A thermostat that's not working correctly might fail to initiate the cooling cycle or might randomly shut off the AC. This erratic behavior can be due to electrical issues or miscommunication with the AC unit.
If the thermostat is set for cool, verify that the furnace door is securely closed and that the furnace's power switch is set to On. Make sure the furnace circuit breaker switches are on. In most cases, your thermostat turns on the compressor and fan (Y and G terminals/ wires) during cooling.
There are a number of reasons why your air conditioner might be running but not cooling. It could be an issue with the thermostat, the compressor, or the evaporator coils. Or, it could simply be clogged with dust and debris, which is preventing it from working properly.
Faulty or Malfunctioning Thermostat
If your thermostat clicks repeatedly and your AC doesn't turn on, it usually indicates that the problem is related to the thermostat itself and could be caused by either an issue with the thermostat relay or the system's wiring.
Some possible solutions include resetting the thermostat to factory settings, checking the circuit breaker, replacing the air filter, checking the outdoor unit, checking the indoor unit, replacing the thermostat's batteries, and checking the connections and wiring for any damage.
Press the reset button. Most models require you to hold the button down for 3-5 seconds before releasing. Restore power to your AC. Restore power to the unit at the circuit breaker, and make sure the unit is set to “on” and your thermostat is set to “cool.”
Most modern thermostats will have a clearly marked reset button inside the panel. It's usually small and recessed, so you might need a pointed object like a paperclip to press it.
Sometimes, the thermostat simply has dead batteries or a wiring issue that is preventing it from sending the correct signal to the AC unit. Replacing the batteries or checking the wiring may solve the problem. If the thermostat malfunctions completely, it may need to be replaced to restore the AC's functionality.
The “Heat” button activates the heating system, whereas the “Cool” button will turn on your AC. The “Off” setting turns all temperature systems off. The “Auto” setting is only available on certain thermostats and regulates the temperature systems according to your program schedule settings.
Turn your thermostat to the 'off' position... Then venture off to your home's breaker box. Find the breaker to your HVAC system, flipping it 'off'. Make sure the breaker is flipped all the way 'off,' then wait for 30-seconds. Turn the breaker back 'on.
For Latest Honeywell Scanners:
Use the single bar code 'DEFALT' command to reset the device. Note: This selection erases all settings and resets the scanner to the original factory defaults.