Why is my furnace blowing cold air? Troubleshooting Your Heating System.

New Jersey weather likes to play with our sensibilities. Sometimes our heating systems do too.

Occasionally we come home to our house in Woodbridge, NJ to find it ice-cold in the dead of winter, or we’re already home and hear that common “click” of a thermostat telling us that warm air is about to start. But we only feel a cool breeze where warm air should be flowing.

Sure we can hear the fan turning and we know something is working but the house isn’t getting warm.

This could be one of several issues with your home heating system.


First, as usual, look for easy solutions. Check the thermostat. As seasons change, we sometimes don’t select the right setting. Maybe the thermostat is still set to “ON” for the fan setting instead of “AUTO.” With the ON setting, the fan will still blow even if the heating element is not working to produce heat.


The next easiest component to inspect in your home heating system is the system’s filters. Some homes have more than one filter, so don’t ignore any of them. A clogged filter can create heat buildup inside an HVAC system by blocking the flow of air over the heat exchanger. This could cause the system to overheat; thus, tripping a high limit switch that shuts down the system.


You might not have one in your heating system, but if you do, check the pilot light. Many older systems use one. You can reignite the pilot light yourself using a long handle lighter or even a match. 

Be sure to turn off the power to the furnace before you attempt to relight the pilot light. And follow the manufacturer’s directions for lighting it. If you’re not comfortable doing this, contacting your trusted service technician at Temp Control is a safe bet. 


Some furnaces have a pipe or hose that transports water away from the unit. This condensate line can get clogged, forcing water to back up into the furnace, causing it to shut off the burners. Check around your furnace unit. If there’s water on the floor, this could be a clogged condensate line. Again, this is a process you accomplish on your own using a snake or sucking a clog with a shop vac. But calling a trusted HVAC technician is always a good bet if you’re not comfortable unclogging the line.


This does not happen often, but a significant leak in your ductwork can make it seem like the system is only blowing cold air. Maybe a duct in the attic has somehow loosened up or a seam has pulled apart. This would obviously suck in cold air from other parts of the house, like the attic or a basement, delivering cooler air than what is set in the thermostat.

If you’ve examined the HVAC system for the above remedies and it’s still blowing cold air or the air doesn’t seem as warm as it should be, having Temp Control’s pros come in and squirm around your attic or other crawl spaces is the best bet.  We serve customers in Middlesex County, NJ, including Woodbridge, Iselin, Colonia, Edison, and Metuchen.