With how cold it can get during the winter in Wisconsin, it’s crucial that your furnace always works when you need it most. Having your furnace suddenly no longer turn on can be a major hassle and will often require an emergency service call. That said, there are some things you can quickly check before making the call, as you might be able to fix the problem yourself without needing to pay a professional.
Thermostat Settings and Functionality
The first thing to check if your furnace won’t turn on is that your thermostat is still working and set to the correct settings. If the screen is blank, it either means that the thermostat is dead or isn’t receiving power. If your thermostat has batteries, you should replace them to see if the screen then comes on. You should also replace the batteries if the screen is showing low battery, as low battery power can sometimes result in a thermostat only working intermittently.
Many newer thermostats, especially smart thermostats, don’t have batteries. Instead, they receive power directly from the HVAC system through the common or C-wire. In this case, a blank screen can indicate that the HVAC unit doesn’t have power. Another possibility is that the C-wire is damaged or has come loose.
Circuit Breaker
The next thing to do is go to your main electrical panel and check the breaker for your furnace to make sure it’s not tripped. If a furnace blower is malfunctioning, has to work harder than normal, or its motor is wearing out, it can sometimes draw excess power and cause the breaker to trip. A frayed wire or loose electrical connection can also cause a short circuit, resulting in a power surge that trips the breaker.
If the breaker is tripped, your furnace should turn on fairly soon after you reset the breaker. If it then runs like normal, you should continue to monitor it to make sure that the breaker doesn’t ever trip a second time. It’s important that you call for an inspection and leave the breaker off if it does trip again. Having the breaker continually trip can be a sign of a serious issue that could result in major damage if you keep trying to run the furnace. If the heater is short-circuiting, it could even catch fire due to wiring overheating and starting to burn and melt.
Pilot Light
Pilot lights were mostly phased out in favor of electronic igniters in the mid-1990s to early 2000s as a way to reduce energy waste and make furnaces more efficient. Nonetheless, some homes still have an older furnace with a pilot light. If your furnace does have a pilot light, you’ll want to check that it’s still lit. If you can’t see the flame, you need to first turn the knob to the “off” position, and then wait around 30 seconds before trying to relight the pilot. To light the pilot, you need to turn the knob to the “pilot” position and press it in all the way. While holding the knob in, you then need to press the ignite button with your other hand. Once the flame is lit, you should continue holding the knob in for around 30 seconds so that the thermocouple fully heats up. If you let go too soon, the flame will immediately go out.
You should hear and smell gas starting to flow when you press in the knob. You should also see the igniter sparking and hear it clicking when you press the ignite button. If the gas doesn’t flow, it means either the gas valve is broken or the gas tube is clogged. If nothing happens when you press the ignite button, you can use a match or a stick lighter to light the pilot. If the pilot light won’t stay lit, you’ll need to have a technician clean or replace the thermocouple.
Access Panel
The last thing to check is that the access panel on the front of the furnace is fully closed. All gas furnaces have a safety switch that prevents them from turning on if the access panel isn’t securely in place. If the access panel is loose and doesn’t fully press the switch in, the furnace won’t turn on. Depending on the brand and model of the furnace, the panel is held in place by clips, knobs, or sheet metal screws.
In some cases, a clip or knob can break or come loose. Vibrations can cause a screw to fall out, resulting in the panel no longer being fully secured. If the panel is bent, it also may not fully depress the switch. With older furnaces, it’s somewhat common for the access panel to no longer sit fully tight and frequently come partially loose due to vibrations.
The access panel should be completely flush with the metal around the opening. If any of the corners are sticking out, you may be able to get the furnace to turn on by just trying to push it back in place. If the panel is held in place by screws, you’ll want to make sure that there’s a screw in each hole and that all of them are tight.
You can tell if the issue is related to the access panel by removing it and pushing in the switch with your hand. If the issue is that the panel was loose, you’ll hear the draft inducer fan kick on as soon as you press the switch. The electronic igniter should also come on at the same time or within a few seconds. If you can’t get the furnace to turn on again when you put the panel back in place, a technician can fix the problem by securing the panel with foil tape or screws. If the panel is badly bent, you’ll need to have it replaced.
Other Issues That Can Prevent a Furnace From Turning On
Unfortunately, these issues are really the only things you can check for yourself. If you still can’t get your furnace to come on after checking them, you’ll need to have a furnace technician diagnose the problem. A gas furnace has numerous components that all need to work properly for the unit to turn on and continue running.
Almost all furnaces produced after the late 1980s or early 1990s have a draft inducer that creates negative air pressure and draws the hot fumes out of the combustion chamber and through the heat exchanger. When the thermostat signals the furnace to run, the draft inducer is the first thing that turns on. Once it’s running at full speed, the pressure it creates activates the pressure switch. When the pressure switch activates, the control board sends an electric current that causes the gas valve to open. The electronic igniter or pilot light then ignites the burners. The flame sensor also has to detect that the burners are lit within a few seconds or else the control board will signal the gas valve to close.
It’s fairly common for a pressure switch to break or an electronic igniter to wear out, both of which will prevent the furnace from turning on. The gas valve can also break or get stuck. Other issues you may encounter are a faulty control board or an electrical issue that prevents the furnace from receiving power. If the flame sensor is too dirty or worn out, the burners will light but then go out within a few seconds.
For reliable heating services in Madison, Wausau, Caledonia, or the surrounding areas, look to Southport Home Services. We specialize in furnace repair, but we can also assist with heating installation and furnace maintenance. Our experienced technicians can quickly and accurately diagnose any problem you’re dealing with. We work on all makes and models and provide a 100% satisfaction guarantee on our services. To schedule an inspection and get your furnace running again, contact us today.
