When your furnace has been running throughout this winter season with no problems and then it suddenly begins blowing cold, this is definitely not normal. When a furnace suddenly begins blowing cool air it will leave the home cold not to mention run up your heating bill. Hal Mechanical will help run you through some of the common reasons why a furnace will suddenly blow cold air, and what needs to be done to correct the issue.
Thermostat Set to On
The first step in determining why the furnace is blowing cold air is to start by checking the thermostat. Check the thermostat setting. If it is in the “on” setting it will blow cold air. When set to “on,” the furnace fan will run constantly even when the furnace isn’t creating heat. If this is the case, simply set the thermostat to “auto”.
Dirty Air Filter
An air filter can greatly influence the entire HVAC system. When the air filters are dirty it can restrict air flow to the furnace. This air flow restriction prevents the air from entering the furnace to be heated. However the blower will activate regardless, sending only cold air through the air ducts. If your furnace is producing cold air and it is not the thermostat, the next easy step is to check the air filters and replace them if they are dirty.
Clogged Condensate Drain Line
Furnaces, as they run through their cycle, can and often do develop condensation, which is why an HVAC system always has a condensate line. As condensation builds up, the water will need somewhere to drain out. The condensate line sends the water safely away from the home. However it can become clogged which has its effects. One effect of a clogged condensate line is the cold air you are feeling coming from your furnace. When the condensate line is clogged the water backs up into the furnace which will switch off the burner. No burners means no heat. The condensate line will need to be cleaned by an HVAC technician.
Old Furnace Pilot Light Problems
The pilot light is the first step during the heating process. The pilot light heats or activates the burner in a furnace. If the pilot light goes out, the furnace will continue to run through the cycle but just doesn’t create any of the heat. A pilot light can simply burn out over time and need to be replaced. Other times the pilot light becomes dirty and covered with soot. If the pilot light is dirty it simply needs to be cleaned. The pilot light should be inspected, cleaned or replaced by an HVAC technician.
Interruption of Gas Supply Line to Furnace
For a gas fueled furnace, if there is an interruption in the supply line, it will prevent the furnace from creating any heat. In some cases the gas line may have been turned off and forgotten. Check the gas supply line to the furnace and make sure that the gas was turned off and not turned back on. Worse case there may be a gas leak in which you will smell the gas, alerting you to the issue.