If your furnace is blowing cold air in your home, this is a sign of an issue with the flame detector, gas supply, air filter, pilot light, or condensate lines. Many of these issues are able to be easily solved on your own by sanitizing or replacing components in the gas furnace.
Problem 1: Incorrect thermostat settings The most common reason for a furnace fan that won't shut off or a furnace blowing cold air and won't shut off is the wrong thermostat settings. The solution: Check the thermostat settings. The fan setting should be on AUTO. If it's set to ON, the furnace fan won't shut off.
Therefore, your furnace blowing cold air could result from a clogged or dirty air filter. If you have a dirty or clogged furnace filter, the cool air from inside your home will struggle to travel through it and into the furnace. This means you have insufficient air to heat and redistribute.
Check Furnace Air Filter
A dirty air filter hinders air movement through the furnace. This raises temperatures inside the furnace, and the limit switch shuts heating cycles down if the unit becomes too hot. If you have a dirty filter, replacing the filter typically stops cold air from blowing.
They are designed to keep you very comfortable. To do this, It is designed to maintain the heat but also the number of cycles per hour of the furnace. The furnace should cycle 6 times an hour at 50% heat load. Incidentally, at 100% heat load ie on a very very cold day, it will run 100% of the time.
When a furnace runs constantly, it probably means that something is dirty or clogged. The filter is the first thing you want to check, especially if you do not replace your filter as often as recommended (once a month during the heating season).
Typically, there's a 10 to 15 minutes allowance for this. However, if after this time it's still producing cold air, then there's an underlying problem that needs to be addressed. It would be wise to turn the furnace off and get in touch with a pro immediately for help dealing with the issue.
With a furnace blowing cold air, the first question you should ask is if the furnace has been turned ON. Two thermostat issues that could cause your furnace to blow cold air include (1) your thermostat is still set to COOL, not HEAT and (2) your thermostat fan is set to ON, not AUTO.
If your furnace is blowing cold air in your home, this is a sign of an issue with the flame detector, gas supply, air filter, pilot light, or condensate lines. Many of these issues are able to be easily solved on your own by sanitizing or replacing components in the gas furnace.
Check your thermostat's batteries and replace any that are exhausted or defective. Clean all of the parts of your furnace, especially the ones that are susceptible to dust and dirt. You could also hire HVAC technicians to clean the system thoroughly. Ensure that the gas valve is open and not obstructed by any debris.
The most common reason a heat pump is blowing cold air through your air vents is defrost mode. This is a safety feature to melt frost and ice within the system. During defrost mode your heat pump made switch modes to heat up the outdoor coils. Indoor temperatures will fall because the system is briefly in cooling mode.
Choose "AUTO" for energy savings and "ON" if you want constant air circulation or improved air filtration. Temperatures can soar or plummet depending on the time of year. Throughout the year, it is important to have reliable heating and cooling systems in order to keep your home supplied with cool or warm air.
If your fan limit switch is set to AUTO but the fan continues to run without ever stopping, you'll need to call a professional. Two problems that could cause your fan to run without stopping include: A bad fan limit switch that needs to be replaced. Bad thermostat wiring.
This can happen if the fan limit switch is stuck in the override position. Resetting the limit switch located near the blower fan will stop the fan from blowing unless directed by the thermostat.
Carrier furnaces typically have a small reset button inside the burner compartment. It may be red or yellow and is usually labeled “Reset.” If you're unsure where to find it, consult your furnace's user manual. Hold the button down for about 10 seconds before releasing it.
Three possible reasons the gas furnace is blowing cold air and won't shut off is the gas supply is not feeding the furnace, or it could simply be shut off. A third reason could be due to a blockage in the gas line your furnace is not receiving an adequate supply of gas.
A malfunctioning thermostat: Since the thermostat is responsible for turning your furnace on and off, a malfunction could lead to extended heating cycles or even running constantly. Inadequate home insulation: While almost every home has some form of insulation, it's often not enough for true energy efficiency.
Check your gas line. If it's been damaged, your furnace, water heater or gas stove won't be working. Some gas furnaces have condensate drain lines to help remove moisture. If there is a blockage to the lines, it could deactivate the burners and cause your furnace to blow cold air.
Get your ductwork checked. If your furnace is blowing hot but your home is still cold, it may be a problem with your ductwork. You may have leaky or damaged ducts that are letting hot air escape and cold air in.
Your furnace could be running constantly because either your thermostat isn't set correctly or is malfunctioning and not properly signaling the furnace when to turn on and off.
Dirty, clogged, or blocked coils restrict your outdoor unit's ability to gather warm air from outside. This process often results in your HVAC unit blowing cold air.
THERE IS A PROBLEM WITH THE GAS OR OIL SUPPLY
A propane furnace or oil furnace blowing cold air might indicate a low or empty fuel supply. And, a clogged oil filter can also cause an oil furnace to turn on and blow cold air.
Before you get worried that your furnace is broken, be mindful that your home heating system is actually only designed and sized to operate at a low outdoor temperature of 0 degrees Fahrenheit.
Check the thermostat
Maybe your heater is not blowing hot air even though the fan is running. As a result, any air that blows out of the vents while your heater is off will usually feel cold. In such a case, there could be an easy solution, particularly if your thermostat setting is the problem.