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The online booking feature is no longer available. Please call our office for any scheduling needs. Sorry for the inconvenience.
“Why is my furnace blowing cold air?” is a question I hear often. It’s a legitimate question. After all, aren’t furnaces supposed to blow warm air?
Well yes, that is what they are designed to do. So when someone asks me “why is my furnace blowing cold air?” I know that they have a malfunctioning furnace. Often it is a simple problem to correct. But it could also indicate a more serious problem.
If your furnace only blows cold air when you set your thermostat to heat, it is trying to tell you that something is amiss. Yeah, I know. Furnaces don’t talk. But they do communicate. They usually “tell” us when something is wrong. By acting unusual or making strange noises, it is their way of telling us “I need attention.”
So, why is my furnace blowing cold air? You can watch this short video for some answers. But I’ll dig a little deeper to explain the most common causes as to why is my furnace blowing cold air?
Almost all modern furnaces have an IFC (integrated furnace control) board. And these circuit boards usually have a small LED diagnostic error code light. It will blink a code when something is wrong with the furnace. You can view a photo of a IFC board with a diagnostic light here. These circuit boards are usually mounted on the blower housing behind the blower compartment door.
The furnace should also have a diagnostic error code chart. This chart will indicate via a blinking LED light why the furnace is not functioning properly. The chart is usually located on the inside of the blower door panel, but sometimes you will find them on the front of the door panel. The chart should look similar to this furnace panel error code chart.
If you’re asking “why is my furnace blowing cold air?” you will most likely see an error code indicating an open limit or roll out switch. So what exactly does this mean?
Limit switches and roll out switches are safety controls, designed to shut off the gas to the furnace in the event of over heating. When a high limit temperature or roll out switch trips, it is because the furnace is becoming dangerously hot and needs to cool down. The open limit circuit should turn off the burners yet keep the blower running in order to cool the furnace down.
Some roll out switches have a manual reset button (seen here). Some are auto reset, as are almost all high temperature limit switches. Auto reset limit switches are supposed to reset after the furnace cools down, although I find that often times they don’t. Sometimes tapping on the front of the switch with a small tool (such as the end of a screwdriver) will reset it.
So what causes these switches to trip? If you find that you have an open roll out or limit switch, here are the most common causes that occur.
For more information or if you need to schedule a service on your furnace, you may contact Basset Heating & Air Conditioning at 719-392-0032 or use the contact form here.
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Freephone: 719-212-4761
FAX: +1 800 889 9898
E-mail: support@bassetheating.com
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