No power: If the thermostat isn't working at all, there could be a power issue. Try checking the circuit breaker box or replacing the batteries. Bad wiring: The thermostat may be unresponsive if the wiring has gone bad. Remove the cover and check inside for loose, detached, or corroded wires.
If the thermostat's display is dark, a lack of power may be the issue. 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.
Resetting your thermostat is often all that's necessary to get it working again. A tripped circuit breaker is another common reason why your AC won't turn on. Using too many appliances at once can trip the circuit breaker. This is also common when there are power surges after a big storm.
Press and Hold: Using a small object, press and hold the reset button. The time you need to hold it can vary, but generally, 5-10 seconds should suffice. Wait and Observe: After releasing the reset button, wait for the thermostat to reboot.
Try checking the circuit breaker box or replacing the batteries. Bad wiring: The thermostat may be unresponsive if the wiring has gone bad. Remove the cover and check inside for loose, detached, or corroded wires. If you spot any problems, contact an HVAC technician for assistance.
If your thermostat has fresh batteries but suddenly lacks power, flashes, or isn't responsive to adjustments, it may need replacement. If resetting the thermostat doesn't resolve the problem, you may have wiring problems or faulty components causing your thermostat to not turn on.
Check the Power Source Sometimes the problem between the thermostat and your furnace is as simple as replacing the batteries. Many digital thermostats use standard batteries to power their functions. Also make sure to check there is power at the furnace as well.
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.
The Air Filter Is Dirty
If the thermostat clicks but the AC or furnace doesn't turn on, most often it's because the filter is clogged. A blocked filter will restrict airflow. The particles it's designed to trap eventually clog the filter media, and the system will be unable to generate heat or cool air.
Dead or Low Thermostat Batteries
The first thing to check with any blank screen issue is the thermostat batteries. Most standard digital thermostats contain AA or AAA batteries to operate the display, transmitter, sensors, and programming. Thermostat batteries provide backup power in the event of an outage.
Standard thermostats: Enlist a friend or family member to assist, Position one person by the thermostat and one person by the furnace. Slowly turn the thermostat from off to heat and increase the temperature. Both the thermostat and furnace should make a sound.
A “No power” alert can be caused by the following: The thermostat wiring is incorrect. Your thermostat is connected to a system that requires a C or common wire, but that wire isn't connected. Some systems, including heat-only, cool-only, zone-controlled, and heat pump systems, require a C wire or Nest Power Connector.
Thermostat Auto Mode
Whenever your thermostat reads that the actual temperature inside of your home is above 78 degrees, it will automatically turn on your air conditioning system.
In most cases, installing a new thermostat is a relatively simple do-it-yourself project that can result in improved comfort and convenience and one that can help you save energy.
Check if the wires are properly connected and look for any signs of damage or wear. If you have a battery-powered thermostat, make sure that you've replaced the batteries recently. If your thermostat isn't receiving power, then it may not be able to communicate with your heating and cooling systems.
There are several reasons why your furnace may not turn on. The most common include a broken thermostat, gas line issues, clogged air filters, blocked ductwork, a tripped circuit breaker, and issues with the furnace itself.
This can happen if there is a power surge or if the thermostat is connected to a faulty electrical circuit.
To reset a non-programmable digital thermostat, you'll need to take the face-off and hold the reset button for five seconds. You can also try removing the batteries for five seconds. Both of these methods should result in a reset thermostat.
High temperature readings
The main symptoms of a failing thermostat are related to engine overheating. It can be easily noticed because the temperature gauge in the vehicle will probably read unusually high. This can be caused by the valves being stuck in a closed position.