Furnace Troubleshooting: Common Signs Of A Faulty Fan Limit Switch

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A furnace plays a pivotal role in ensuring that a home is comfortable. Therefore, when your system starts acting up, it can be very frustrating. When this happens, knowing how to detect the source of your furnace problem is important. A malfunctioning fan limit switch is a common cause of furnace problems. The following are tips that will help you determine whether or not it is the source of your problems.

Does your furnace send cold air into your home?

If your furnace sends chilly air into your home when it is supposed to heat it, then you have a faulty fan limit switch. This is because during normal operations, this switch is supposed to keep the blower from starting up for as long as the air in the supply plenum is below the required temperature. By so doing, it prevents the blower from pushing the not-yet-heated air through the duct system and into your home. This then prevents the uncomfortable situation where a furnace sends chilly air into a home.

If the air coming out of your supply ducts is cold, then you are likely dealing with a faulty fan limit switch. Replacing it will prevent this from happening.

Does your heat exchanger show signs of damage?

When a heat exchanger starts to show signs of cracking, then it is likely suffering from overheating. And if this is not corrected as soon as possible, the heat exchanger can become irreparably damaged, necessitating costly replacements.

Since the fan limit switch usually plays a role in controlling the burner, signs of overheating-related compressor damage are reliable signs of a failing fan limit switch. This is because while messed up system controls and blockages in the air duct system may be the direct cause of the overheating, the fan limit switch is supposed to step in and stop the situation from getting worse. This is because this switch has its feelers in the warm air supply plenum. It is supposed to detect the temperature in this area rising and when they get abnormally high, it is supposed to switch off the burner, preventing further overheating. As a result, if your furnace's heat exchanger shows signs of overheating-related damage, you likely have a fan limit switch that has a habit of failing to prevent this type of overheating. Replacing the switch as soon as possible is recommended as doing so will help to prevent further damage. 

For more information, contact local professionals like Allzone Air Conditioning & Heating Corp.