In this article, we’ll review six common reasons why your heater won’t turn on when the weather gets cold. They range from simple DIY fixes to bigger problems that require a professional.
Going without heat can be more than just uncomfortable. You also run the risks of your pipes freezing if it stays too cold for too long. Or, if the system keeps trying to turn on but can’t, a small problem could be getting worse without you realizing it.
Six Common Reasons Your Heater Won’t Turn On
- Thermostat Is Broken Or Set Incorrectly
- The Air Filter Is Clogged
- The Pilot Light Is Out
- The Heat Exchanger Is Cracked
- No Gas Is Coming In
- It’s Too Cold For A Heat Pump
Thermostat Is Broken Or Set Incorrectly
Start by checking that you’ve set your thermostat to “Heat” and “Auto.” If it’s on cooling, then it’s waiting for the temperature to warm to that setting so it can turn on the AC. It’s easy to forget to switch it over after summer.
Also, watch for “Fan Only.” In this case, the fan will blow to circulate air, but it won’t turn on the heater or air conditioning. And, if the settings are correct but it’s not working, try changing the battery.
If the power’s low, then the thermostat may not read correctly, or it won’t send signals to the HVAC system. Or, you can determine if something’s broken with a simple test.
The Air Filter Is Clogged
Your air filter could be clogged with so much dust, dirt, and debris that it’s preventing the system from turning on. Slide out the old filter and replace it with a new one.
You should do this every month regardless of whether there’s a problem. And, take note of the color when you remove the old one.
The screen on the filter goes in white. If it’s grey or dark grey, you left it in way too long, and it got clogged.
The Pilot Light Is Out
If you’re comfortable removing a panel on your furnace, you can check if the pilot light is out. Even if you don’t want to try lighting it yourself, you’ll know what the problem is. And, you’ll want to get it fixed quickly.
When the pilot light is out, gas can build up in your home. It’s still coming in from the supply, but it’s not following the normal combustion process.
Take off the panel and look for a small flame. The exact location depends on the model you have, but it should be visible.
If you can’t see the flame, then it’s out. If it’s a color other than blue, then your unit needs a cleaning.
The Heat Exchanger Is Cracked
The heat exchanger is a ceramic chamber deep inside the system. If it breaks or splits, carbon monoxide seeps out into your home. If it cracks, it can cause a breakdown.
But, you can’t see this piece without taking apart the furnace. So, the signs of it cracking are the heater not turning on and/or the carbon monoxide detectors in your house going off.
With a cracked heat exchanger, air can get in and interfere with the furnace blower. Or, it broke because heat keeps backing up into the system and damaging the ceramic piece. In that case, your furnace keeps shutting off to prevent overheating.
Meanwhile, if that tasteless, odorless gas is escaping into your house, you’ll know from the detectors.
The bad news is that this problem means you need a new furnace. You can click the link below to learn more, but the short version is that it’s difficult and too expensive to fix. And, there’s no guarantee the repair would hold.
No Gas Is Coming In
This is a problem specifically for gas furnaces: There’s a problem with your supply line, and the system isn’t getting any natural gas. With no fuel, there’s nothing to heat.
Start by finding the gas control valve and make sure it’s turned to “On.” Make sure you don’t smell gas — it could be the sign of a leak.
You can double-check by putting some soapy water in a spray bottle and spraying the valve and surrounding areas. If it bubbles, gas is escaping.
It’s Too Cold For A Heat Pump
This is a problem specific to heat pumps and often older models: It’s too cold for them to work.
Despite the name, heat pumps were primarily for cooling. They can always transfer heat out of the house, hence the name.
In the cold weather, they also draw in what little heat is outside, amplify it, and send it into the house to keep you warm. But, older models only worked if the temperature was over freezing.
Any lower than that, and there wasn’t enough heat available for it to work. Today, you can get a Hyper Heat model that functions in freezing, sub-zero weather. But, an older model or one made primarily for cooling will shut off.
How A Heater Tune-Up Prevents HVAC Repair Problems
You can prevent HVAC repair problems in your Havertown, PA home with a tune-up at the beginning of the heating season. Think of it as a well visit for your furnace: A tech checks over everything to make sure there are no problems. They’ll clean out the system and replace anything that’s broken or worn down.
Heating And Cooling Service In Havertown, PA
John Cipollone has provided expert, reliable heating and cooling services in Havertown, PA, and across DelCo and Montgomery County for more than 50 years! Whether you need a repair or want to start the season with a tune-up, you can call or email us to set an appointment.