The thermostat may have a dead battery, so replace them with fresh ones and try again. Your furnace may turn on right away after this. If it doesn't, you may have a faulty power circuit. Have an HVAC professional diagnose this issue, and provide you with professional recommendations.
If your furnace won't kick on when you turn the thermostat up, it could be due to a variety of reasons such as a tripped circuit breaker, a faulty thermostat, or a problem with the furnace itself like a malfunctioning igniter or gas valve. Checking these components might help you figure out the issue.
Furnace Not Igniting Because of Incorrect Thermostat Setting
Make sure the thermostat is set to heating and that the temperature is set high enough to actually turn the furnace on. It may be set at too low of a temperature to activate the furnace.
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.
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.
If nothing's happening when you're expecting the whir of a blower, check the circuit breaker and fuse. At your electrical panel, make sure all switches related to the HVAC system are on. Reset any tripped breakers and replace all blown fuses, and your furnace should kick back on.
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 your boiler stops responding to your thermostat or heating controls, it's worth checking the batteries. Not all thermostats use batteries - some are wired into the mains but have backup batteries in case your power fails. If you've experienced a power cut, your thermostat's backup battery might've run out.
Most likely, your furnace is making a clicking noise and not providing heat because your furnace's spark igniter is trying to ignite your pilot light or burners but is failing to do so. In other words, there's an ignition system malfunction that needs to be fixed. Otherwise, your furnace won't start.
Checking your thermostat is the best place to start. Make sure it's set to “heat” and that you've set the temperature higher than the current room temperature. If that doesn't resolve the problem, try switching your fan to “on” to force the furnace to start working.
Defective Igniter or Pilot Light
If it clicks but your furnace won't ignite after the combustion cycle, the electronic ignition systems probably need to be replaced. In cases where the furnace ignition starts normally but only stays on for a few minutes and then goes out, a new pilot light likely needs to be installed.
If the wiring between the thermostat and the air conditioning system is faulty, the system may not turn on. This can happen if the wiring is old or if it has become damaged over time. To fix this issue, you may need to call a professional HVAC technician to inspect and repair the wiring.
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.
Only an HVAC professional can diagnose the root of AC repair problems and offer technical solutions for them. On a side note , if there is a problem with your system's auxiliary heat, this will be displayed on the thermostat.
There is usually a small reset button somewhere on the thermostat. Finding this button may require that the thermostat panel be removed and pressing this button may require something like a paperclip to push. Hold the reset button down for 5 seconds and the thermostat should reset.
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.
Possible reasons include thermostat issues (incorrect settings or dead batteries), power problems (tripped circuit breaker or blown fuse), and furnace malfunctions (dirty air filter, faulty ignition system, or tripped safety switches). Checking these areas can help identify the issue.
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.
The cause of your furnace not blowing hot air could be the thermostat configuration, a dirty air filter, the high limit switch, a clogged condensate line, insufficient fuel, leaky ducts, ignition problems, a blocked burner, flame sensor issues, gas valve malfunctions, a cracked heat exchanger, or a clogged coil.
Thermostat issues are one of the most common culprits of furnace malfunctions. If your furnace isn't working as well as it should, and you've determined that other issues such as a faulty furnace heat exchanger or dirty air filters aren't to blame, you should inspect and troubleshoot your thermostat.
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.
If your furnace turns on but no heat is produced, there may be a problem with the fuel supply or the ignition system. If something is stopping your furnace from receiving gas, there is no fuel to combust so the furnace will not create any heat. The furnace turns on but no heat comes out.
Uneven Heating
Inconsistent heating patterns often point to thermostat inaccuracies, as the device struggles to regulate the temperature evenly. On the other hand if the entire house feels uniformly cold then the furnace might be the problem.