Faulty High Voltage Wire An issue with the high voltage wire may be the cause of a malfunctioning thermostat. If there is a problem with the high voltage wire, the thermostat will not be able to signal the HVAC system properly. A high-voltage wire that is damaged, loose, or disconnected causes thermostat problems.
Remove the batteries and put them straight back in again. This will turn the thermostat off and on which should help establish a connection to the receiver. Place the thermostat back on the wall. The thermostat should then display a 'Reconnecting' message.
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.
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.
Place the multimeter's red probe onto the thermostat terminal marked R for red; you can place the black probe onto any of the other terminals. The multimeter reading should be at or close to the thermostat's voltage level.
Faulty Wiring or Equipment: Bad wiring can prevent power from reaching your thermostat. It can also increase the risk of a short circuit or fire. Check whether the thermostat's wiring is frayed, broken, or installed incorrectly (the wires/terminals are usually color-coded).
Turn off the furnace's circuit breaker. Untwist the “R” and “W” wires, remove them from their connectors, and then twist the wire ends together. Turn on the furnace's breaker. If the light comes on, it shows that the thermostat is not sending a signal to the furnace.
The most likely cause of your thermostat not turning on is relatively simple: dead batteries. The solution is equally simple: try replacing the batteries to see if your thermostat powers back on. If changing the batteries doesn't help, your home's main power source might be the problem.
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.
An issue with the high voltage wire may be the cause of a malfunctioning thermostat. If there is a problem with the high voltage wire, the thermostat will not be able to signal the HVAC system properly. A high-voltage wire that is damaged, loose, or disconnected causes thermostat problems.
If your wires are connected but your thermostat still isn't working properly, that means it's time to hire a professional. They'll open the thermostat and test the wires individually to see which one is faulty. Since messing with wires is dangerous, you'll want to contact a certified HVAC technician.
Loose wiring in your thermostat can disrupt its ability to communicate with your HVAC system, leading to erratic behavior or a complete shutdown. Should you detect irregular heating or cooling, abrupt system malfunctions, or your thermostat going utterly blank, loose wiring might be the root of the thermostat problem.
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.
Check the batteries in the thermostat
It sounds so obvious but this is a really common thing. Being wireless, the sole power source for the thermostat is its batteries and they don't last forever. Try changing the batteries and then turn the heating on.
The thermostat needs to be recalibrated.
Sometimes, your furnace or AC system won't hit the thermostat temperature because the thermostat isn't correctly calibrated. This can be a common issue with new thermostats, and also often occurs after a power outage or when the thermostat's batteries are running low.
A quick fix to restore your thermostat's power is a tripped circuit breaker or blown fuse, depending what you have in your home. Sometimes a surge can cause this issue. If you check your electrical box and a circuit breaker is tripped, just flip it back. If you have fuses, replace the fuse.
Turn your thermostat “off”, then flip the related circuit breaker “off”. Wait 30 seconds, then turn the breaker back “on,” then the thermostat. Set the thermostat to hot or cold, whichever you prefer, and your desired temperature. This should effectively reset it.
HVAC System Suddenly Quits Working
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.
Your Thermostat Is Off or Needs New Batteries
So, be sure to double-check that your thermostat is on and appears to be functioning as normal. Even if everything looks good on the surface, another DIY step worth taking is to replace your thermostat's batteries.
When you set the thermostat above or below the current room temperature, you should hear a click, and the AC or furnace should kick on almost immediately. If you make changes at the thermostat and nothing happens, that's the first sign you have a bad thermostat.
Check the circuit breaker panel.
The next simplest solution for a thermostat that has no power is a tripped circuit breaker. This is a common cause for appliances, power outlets, and HVAC equipment not working. Open your electrical panel and look for a switch that is not aligned with the rest.