If your furnace is blowing cool air, you may want to check the limit switch. It’s a dual-purpose device that controls the blower and protects against excessive hot temperatures. While limit switches can fail in different ways, some forms of failure can result in cool air coming out of the supply vents.
What Is a Limit Switch?
A limit switch is a device that controls a furnace’s blower and burner assembly. It’s typically found inside the air handler or the furnace itself. The limit switch will tell the blower to activate at a specific temperature. It will monitor the temperature inside of the furnace, and after the furnace has heated up, the limit switch will send the signal to activate the blower.
In addition to controlling the blower, the limit switch will shut down the burner assembly if the furnace gets too hot. Limit switches work by monitoring the temperature inside the furnace. Furnaces are designed to operate within a specific temperature range. If they exceed this range, they could sustain damage.
How a Bad Limit Switch Can Cause Cool Air
Your furnace’s blower may turn on prematurely if the limit switch is bad. Even if it’s working as intended, you won’t immediately feel warm air coming out of the supply vents after turning on your furnace. Rather, there’s a short delay, which is achieved with the limit switch.
A bad limit switch may eliminate this delay. The limit switch may assume your furnace has already reached its operating temperature when your furnace is still cold, so it will send the signal to activate the blower. The blower will then circulate cool or room-temperature air through the ductwork.
Replacing a Bad Limit Switch
Some limit switches can be repaired, but replacing them is typically the best solution. They are small, inexpensive devices that are easy to replace. You just need to remove the old limit switch from your furnace and replace it with a new one of the same type. Alternatively, if you can’t locate the limit switch, or if you’re not comfortable handling it, you can contact a professional.
Don’t wait until the middle of winter to get your furnace’s limit switch replaced. If it’s making your furnace blow cool air, it’s costing you money in wasted energy. To make matters worse, a bad limit switch can place your furnace at risk of overheating, which can lead to even more costly repairs. You can avoid these furnace-related problems by replacing the limit switch as soon as possible.
If you are experiencing a problem with your air conditioning or heating call us at 512-336-1431 to schedule an appointment. We’ll be glad to come out and take a look at the issue.
1431-183 A/C & Heating proudly serves Round Rock, Georgetown, Cedar Park, Pflugerville, Leander, Liberty Hill, and North Austin.
