The air filter is too dirty and too full of debris. Your flame sensor isn't working. The thermostat is in the wrong spot. Your Furnace is too big for your home.
A clogged filter can prevent air from flowing into your heating system and cause it to stop working. Oftentimes, switching out your dirty air filter with a clean one can restore heat to your home.
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.
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.
If your heater doesn't start, chances are the problem stems from having a dirty furnace. Having dirt on your blower motor or flamer sensor could render your furnace unable to perform. When the blower motor is too dirty, it won't pass enough cool air to the heat exchanger, leading to equipment failure.
A Recap of Why the Thermostat Says Heat On But No Heat Comes from the Furnace and What to Do About It. Dirty air filter–Change it. Gas supply turned off–Turn on the valve or call the gas company. Incorrect thermostat settings–Review all the settings and change them if necessary.
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 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.
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.
Check Thermostat Settings: Ensure the thermostat is set to “heat,” and the fan is on “auto.” Inspect Air Filter: Replace a dirty or clogged air filter with a new one. Relight the Pilot: If you have a pilot light, follow the manufacturer's instructions to relight it.
To reset mechanical thermostats, simply turn off the thermostat and flip the circuit breaker. This can be done by going to the breaker panel and turning off the appropriate breaker switch for 30 seconds. After turning the breaker back on, turn the thermostat back on and the thermostat should be reset.
Some of the most common thermostat issues include:
The thermostat is broken, not properly level, or dusty. The thermostat needs to be recalibrated. There is loose wiring causing a thermostat issue. The thermostat is not in an ideal location in your home.
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.
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.
In most newer systems, the button is often directly next to the blower motor, while in older systems, it may be harder to spot as it is sometimes underneath or behind the motor. The reset button is often made of yellow or red plastic and marked with a large “R ” to make it easier to spot.
If your thermostat won't turn on the heat in your home, change out the batteries and see if that fixes the problem. If not, your faulty thermostat could be the result of the following: A tripped breaker. Loose wiring.
This can occur if there's a malfunction in the furnace's components, such as a faulty limit switch or a blocked heat exchanger. In such cases, it's crucial to consult a professional HVAC technician for a thorough inspection and necessary repairs.
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.
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.
A clogged filter is probably the most common reason for this problem, so it's a good place to start investigating. Take a look at your filter and, if it's really dirty and clogged, it means there's restricted airflow to your furnace. This may be keeping it from being able to create heat.
The average cost of a new thermostat, including installation, ranges in price from $50 to $500 or more based on several factors including the type of thermostat, labor costs, the complexity of the installation, and more.
To confirm that it is most likely a boiler thermostat problem, shut down the system, turn the temperature on your controller down to zero, and do the same with any in-room thermostats if you have them. Turn it on again, but keep your hot water off so you can check the central heating first.