Before you do any work on a furnace, make sure power and gas are turned off. Also, note the make, model number and serial number on the label so you can get replacement parts if needed.
The first common furnace problem is a dirty air filter. This limits the amount of hot air that blows out your vents, leaving you chilly.
1. Check the Thermostat
The first thing you should do if your furnace isn’t heating is to check the thermostat. Make sure the thermostat is set to “heat,” and that it’s at least five degrees higher than room temperature. It may seem silly, but you would be surprised how many service calls are made without checking this.
You should also make sure the thermostat battery is fresh. If the batteries are low, the thermostat may not be getting the signal that it needs to turn on. Next, you should try initiating a furnace turn on by manually raising the temperature setting on the thermostat. A properly functioning thermostat should respond immediately to this demand by making a clicking sound and turning on the blower motor.
If the thermostat is turning on the blower but not igniting the furnace burner, you may need to open up the ductwork and inspect it for debris, blockages or leaks. Be sure to remove all the dirt and dust from any registers in your home, and make sure that the ducts are all sealed properly with metal duct tape (not standard cloth duct tape). You should also make sure that no dampers or air conditioner bypasses are closed.
To inspect the thermostat itself, shut off the power to the unit by switching off the breaker that controls it. Remove the thermostat cover and take a picture of it to reference later. With the power off, you can then unscrew the terminal screws and pull the wires loose, making note of which ones are connected to which terminals. If you’re not comfortable working on electrical wiring, have a professional do this work for you.
2. Check the Thermostat Batteries
Some thermostats have wires that connect to the house’s electrical system, while others use batteries. If yours uses batteries, check the battery indicator for a low charge. Then replace the battery and re-test it. Also, if your thermostat is electronic or programmable, double-check the date and time settings to make sure they’re correct.
If you have a gas furnace, also check the pilot light. The flame should be blue; if it’s yellow, the gas may not be burning properly. Also, check the ductwork for leaks. Sometimes people close a vent or air return to do a DIY repair and forget to reopen it, so the heat can’t reach that area of the home.
It’s always a good idea to get in the habit of replacing your furnace batteries and carbon monoxide detector batteries every year around the start of fall, or as advised by the manufacturer. This can prevent a minor problem from turning into a major one.
To change the thermostat batteries, pull up on the wall-mounted base plate and then slide the housing off. Take out the old batteries with your hand or a flat-head screwdriver. Replace them with new ones, making sure the plus and minus ends are aligned correctly (if they are marked). Then place the housing back onto the plate and flip it shut or snap it into place.
3. Check the Thermostat Wires
Thermostats and their wiring can be tricky to work with, so it is always best to use caution when performing any maintenance or repair on your own. This includes turning off power to the thermostat and system control board before you begin working, especially if you aren’t sure what you’re doing. It’s also recommended that you take a photo of the thermostat wiring before beginning and familiarize yourself with color coding so you can identify each wire.
To access your thermostat’s wiring, you will first need to remove the faceplate of the thermostat from the wall. You should then reveal four or more wires connecting to screw terminals on the thermostat sub-base. These wires will be labelled as R (red), W (white), G (green) and Y (yellow). Some thermostats only connect red and white, while others may also connect red and green. Once you’ve identified the wires, disconnect them from their connections by loosening the bolts. Be careful not to let the wires fall into the hole in the wall (wrap them with a pencil if needed).
When you’re ready to test your thermostat, you can do so by setting your multimeter to AC voltage mode and placing one probe on each of the wires. Then, use the other probe to touch each terminal on the sub-base of your thermostat to make sure that the voltage is reading correctly.
If you’re unable to locate the source of your problem, it might be time to call in a professional for assistance. There are many common furnace related sounds that can be a sign of an issue, including scraping noises from the ductwork expanding and contracting as it heats and cools, rattling noises from loose panels and squealing noises that could indicate a belt has slipped. To learn more about these and other potential issues, check out this list of furnace sounds from The Spruce.
4. Check the Thermostat Settings
When the temperature isn’t registering right, it could be because the thermostat isn’t calibrated properly. A little bit of adjusting the thermostat can fix this problem. If you’re comfortable removing the cover to expose the wiring, try moving the thermostat dial up or down by one calibration mark. This should make a noticeable difference in the reading on the thermometer.
Make sure the heating mode is set to “heat.” This may sound obvious, but it’s important that you double check the settings. Oftentimes, homeowners forget to change the mode on their heater, which leads to wasting energy.
If the furnace still isn’t working, it could be because of a power outage. You’ll want to confirm that the furnace switch is on and there’s power at the electrical panel. If you’re not sure, go to the breaker box and look for a circuit that controls your furnace, and make sure it isn’t tripped or blown.
If a gas leak is present, you’ll need to call a professional immediately. A leak in the system can lead to carbon monoxide poisoning, which is dangerous for everyone in your home. Gas leaks can also cause fires. If you see or smell a burning smell, turn off the furnace and open doors and windows to vent it out.
Keep up with routine maintenance on your heating system to avoid these common repairs. Warner Service writes articles about regular maintenance practices that extend the life of your equipment, save you money, and prevent dangerous problems such as carbon monoxide production. If you need help with your furnace, contact a professional company that specializes in heating repair services. They have a wide variety of experience and can diagnose and fix any issue with your system.
5. Check the Thermostat Settings
Furnaces are the heart of your home’s heating system. These vital appliances generate heat that is sent through your ductwork to different parts of the house. But, like any appliance, your furnace can sometimes break down or stop working properly. With some know-how, you can do a few simple steps to troubleshoot and repair your furnace.
The first thing to check is whether the thermostat itself is still powered. If the screen isn’t on, or if it shows an unfavorable temperature setting, the thermostat has most likely lost power. In this case, you can try flipping the breaker that controls the HVAC unit to restore power.
It’s also important to check that the “heat” setting is actually on. If it’s not, you can usually set the correct setting by pressing and holding the “set” or “program” button and using the up and down arrows to move through the various options.
Another common problem is a miscalibrated thermostat. This can cause the reading on the thermostat to be off by a few degrees, which is enough of a difference to cause problems with your home’s heating system. This can be corrected by adjusting the thermostat’s heat anticipator.
Rumbling or squeaking noises from your furnace aren’t normal and can indicate that the pilot light needs to be relit or that the blower motor lubrication ports need oiling. This isn’t an easy task, however, and it may require a professional technician to fix.
Taking care of maintenance on your furnace is essential to keeping it running correctly, but it’s easy for these tasks to fall by the wayside as your busy life takes over. By following these tips, you can keep your furnace running efficiently for years to come and reduce the risk of an unexpected breakdown in the middle of winter.