One of the most frustrating issues you can face in your home is finding yourself with a furnace blowing cold air. There are, incidentally, some common causes for why your furnace may be blowing cold air instead of warm, and what you can do to fix the problem.
Check if your thermostat is set to ON instead of AUTO.
If you’re noticing that your furnace starts blowing cold air here and there, not consistently, it may be because your thermostat is set to ON. This means that the fan is what’s working consistently, not your actual furnace heating the air. Simply switch your setting to AUTO, and your fan will work when your furnace does, maintaining the temperature you’ve set for your home. You may also be experiencing issues with the battery in your thermostat, so replacing those could fix your issue as well.
Your furnace’s pilot light has gone out.
This is mainly for older systems. If you have a newer system, it likely uses an electric ignition system. This still could be the cause of the problem because they do need replacement every few years, but older systems have a pilot light that might actually need to be re-lit.
If this is the case and you’re comfortable relighting it on your own, ensure that gas is flowing through and carefully relight the pilot. If you are unable to, or the light goes out soon after you’ve lit it, you may need to have repairs done to your furnace, or a cleaning done soon to ensure that the light will work properly.
Your furnace may have overheated.
If everything seems to work properly, and then your furnace blows cold air back and forth until it switches off, you may be faced with a furnace that has overheated. Your furnace’s limit switch, which specifically works as a safety measure, has turned your furnace burners off until the unit reaches a safe temperature. The main cause for this problem is having a dirty air filter. Properly clean or exchange your air filter for a new one, and see if your furnace begins working again.
High-Efficiency Vent Pipes are Blocked
On most high-efficiency furnaces, there are intake and exhaust PVC pipes that lead from the furnace to outside. Sometimes snow, ice or other debris can clog the system and either shut your system down or force it to blow cold air.
It’s important to have a professional do cleaning and maintenance on your furnace annually, to ensure that the problems you may come to face are minimal. A lot of issues and repairs to parts can be caught early on by our licensed technicians. In those cases, the cost for repairs will be significantly less than if your furnace broke down completely, so it’s definitely beneficial to have someone come look over your unit!