You turn on your furnace during a cool San Marcos evening only to find it blowing cold air. Is this a significant problem, or is there a minor solution to ensure your home stays warm during the winter? The following are some reasons why your furnace might be blowing cold air and some steps our HVAC technicians at Oak Island Heating and Air Conditioning may take to get your furnace working again.

Start With Some Basic Troubleshooting

You can do some basic tests to narrow down the problem before you call an HVAC expert for help. Start by looking at your thermostat. Make sure that it is set to the correct mode and proper temperature.

If your thermostat is set to “cool,” turn it to “heat” mode. Check the temperature settings on your programmable thermostat, as it may have been improperly configured during the initial setup. Another common thermostat issue is that the thermostat is set to “on” instead of “auto.” The blower fan constantly runs, even if the thermostat has told the furnace to disengage the burners. When this happens, the fan circulates cool or room-temperature air through the house.

If the thermostat is set right, check your furnace. Is it making strange noises or producing out-of-the-ordinary smells? If your furnace won’t turn on, or if it’s making weird noises, there is an issue that will require an HVAC professional to address.

Check for Common Thermostat Problems

The location of your thermostat in the house could cause your furnace to blow cold air. It should not be in direct sunlight. If it is, the thermostat will register that the house is a lot warmer than it is, so your furnace will not run hot enough.

Like other appliances, your thermostat needs periodic cleaning. If the contacts of your thermostat are dirty, it will not correctly gauge the temperature of the air in your home and may not alert your furnace to activate when the temperature in the house drops.

A battery-powered thermostat can run on batteries for years, so you may not notice that the batteries need to be replaced. Without proper power, your thermostat will have difficulty keeping your home at the appropriate temperature.

Finally, if your thermostat was improperly installed or wires are loose or improperly connected, the thermostat may be fried or not be sending signals to your furnace to activate. You do not want to try to repair or replace the thermostat yourself. It’s best to contact our team at Oak Island Heating and Air Conditioning, and we will ensure that your thermostat is installed correctly, cleaned, appropriately programmed, and installed in the ideal location.

Reasons Why Your Furnace Is Not Turning On

There are several reasons why your furnace may not turn on, causing your blowers to move cold or room-temperature air around the house.

First, check the furnace’s power switch located next to the furnace on its side. It will look like a light switch, and you want to ensure it is in the “on” position. If the system still does not start up after turning on the power, this could indicate a blown or tripped circuit breaker.

If the fuse or circuit breaker is tripped, the furnace is not getting electricity, so you will need to reset the breaker box. There is likely an electrical issue if the circuit breaker trips again. At this point, it’s best to leave the unit off and contact HVAC professionals for help.

Check to ensure that the gas line to the furnace is on. The handle should sit parallel to the gas line if it is on. If it’s perpendicular, the gas has been turned off. Rotate the gas valve handle parallel to the gas line and test to see if the furnace is working. If the gas line is on, the unit has power. If it is still blowing cold air, a more complicated issue will require an HVAC tech’s assistance.

The Results of a Damaged or Faulty Blower Motor

If you feel cold air or no air at all, your blower motor could be faulty or dirty. The motor pulls air from outside your home and moves it through the furnace through your duct system to heat the house. When there is little or no airflow, the furnace cannot operate. It will shut down.

If the motor is extremely dirty, it may be able to push air, but it will struggle to move enough air over the heat exchanger for optimal performance. The air that makes it to your heating vents will be lukewarm or cool. The heat exchanger could overheat with time, causing the entire unit to shut down. Dirty or faulty blower motors are not something to take lightly.

The best way to prevent this is to schedule annual maintenance with an HVAC technician. During the maintenance, the technician will evaluate the blower motor, clean its moving parts, and ensure that it is adequately lubricated. This way, every time you flip on your furnace, you will enjoy a steady stream of properly conditioned air.

Make Sure You Check the Pilot Light

Check the pilot light if you have an older gas furnace blowing cold air. Your pilot light is what ignites the burners to produce hot air. If there is no pilot light, there is no heat, so the blowers are circulating cold air.

A dirty or bent thermocouple could be the culprit. While cleaning and servicing the thermocouple, your HVAC professional may realize that it’s broken and needs to be replaced.

The pilot light is fed gas through a tiny opening that can become clogged. The pilot light should burn bright blue when the opening is unobstructed and clean. When it is dirty, the pilot light will burn red or yellow. A red or yellow flame is not hot enough to adequately heat the thermocouple, and a filthy pilot opening could prevent enough gas from getting through.

Finally, your furnace may have been installed in a small space where there’s not enough oxygen for the pilot light to use to burn. This is dangerous because, in addition to the pilot light constantly turning off, carbon monoxide could build up in your home. If you suspect this is the reason for the issues with your pilot light, talk to our team about relocating the furnace immediately.

Flame Sensor Malfunction

In a gas furnace, the flame sensor prevents gas from flowing in your furnace if there is no flame. If the flame sensor detects that the burners are not ignited, it automatically turns off the gas flow to protect your health and home. Flame sensors can crack and become damaged because they are subjected to intense heat inside a furnace. The good news is that it is relatively easy for an HVAC technician to replace the sensor and get warm air flowing through your home again.

HVAC in San Marcos and the Surrounding Area

At Oak Island Heating and Air Conditioning, we have been providing HVAC service in the San Marcos area for over two decades. We are Better Business Bureau accredited, and our technicians are NATE certified. We prioritize training and are happy to be leaders in the HVAC field.

Our services include HVAC installation, maintenance, and repair. We install heat pumps, whole-house fans, and humidifiers and design new HVAC systems. Contact Oak Island Heating and Air Conditioning today, and let your local, friendly HVAC experts get your furnace blowing warm air again.

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