Is Your Furnace Blowing Cold Air?


Is Your Furnace Blowing Cold Air?

What to Do, What to Look For.

Winter in New Jersey is not the time to have a furnace blowing cold air! If this is happening in your home right now, your HVAC system isn’t doing its job properly. There are several reasons why and some issues to investigate, for heating systems fueled by natural gas. These systems may run on forced hot air, hot water, or steam.

First (and it seems obvious but …) check that your thermostat is set to “heat.” Set the temperature a few degrees higher than the current room temperature to make sure the furnace goes on. If that doesn’t solve the issue, check that the furnace emergency shut-off switch is in the “on” position. Also check the circuit breaker for the furnace.

Should these simple DIY checks fail to solve the cold air problem, it could be that:

  • The thermostat is broken (either misreading ambient temperature or no longer communicating with your HVAC system). Check the batteries if present and replace if necessary.
  • The ducts or vents are blocked
    An obstruction or blockage will restrict airflow and cause your HVAC system to blow colder air. Check that your vents are fully open, and that furniture or other household objects are not blocking them.
  • Dirty air filter
    Clogged and dirty air filters don’t allow hot air to flow from the furnace through the ductwork and into your home. You can clean and change your filter regularly (at least every three months). Clean filters are part of maintaining your HVAC system’s efficiency and performance. During your routine fall maintenance, your Bloomfield Cooling, Heating & Electric technician will replace air filters and perform all necessary point checks and cleaning to avoid this problem.
  • Not enough air from the return vent
    The return vent draws air from your home into the air ducts and to the furnace for heating. If the return vents are blocked by an object, that indoor air won’t get to the furnace to be heated to keep your home warm.
  • The furnace ignition is not starting
    If the burners are not being activated, a broken pilot light (the small flame in older systems) or electronic furnace ignition would be the culprit. No ignition, no fire, no hot air. Relighting a pilot light is relatively easy for many homeowners, but a busted electronic furnace ignition requires replacement by a certified HVAC technician. If the pilot light keeps going out, call us to investigate.
  • The furnace has a faulty circuit control board
    The circuit control board communicates with the thermostat, and relays heating instructions to the furnace blower and burner. If the circuit control board isn’t working, it might need cleaning and maintenance. Beware: if the furnace is leaking water, that moisture could drip onto the control board, disabling it. Therefore, if you see water leaking from your heating system, call Bloomfield Cooling, Heating & Electric right away.
  • Insufficient fuel supply
    If gas isn’t getting to the forced hot air furnace, we can check your gas valve. But you might need your local utility to check your natural gas line. If your system uses propane as a fuel source, it might be time for a tank refill.
  • Faulty or overheated main limit
    The main limit switch is inside the furnace. When it overheats, it activates a safety mode to shut off ignition as a safety feature. The cold air could indicate that the furnace is overheating; this requires immediate attention. The main limit switch may also be dirty, broken, or past its prime and ready for replacement. A properly functioning main limit switch does not shut down the ignition process unless overheating is truly the issue.
  • The heat exchanger is cracked
    The main limit could be overheating due to a cracked heat exchanger. This can cause cold air to come from the vents. A cracked heat exchanger is a dangerous matter as it can lead to carbon monoxide poisoning.
  • Improperly sized ductwork
    Ductwork must be properly sized for your home in order to deliver the required amount of air to each room. If the return ductwork is too small, and therefore cannot take in the required amount of air for heating, you’ll be chilly! When we design HVAC systems, we take into account the entire square footage of the house and the size of the individual rooms to compute the right ductwork size.
  • Clogged evaporator coil
    On a central HVAC system, the evaporator coil in the cooling system can cause the furnace to blow cold air. That’s because this component is located above the furnace. All treated air passes by the evaporator coil to enter the supply duct. A clogged or dirty coil will make that passage difficult or can completely obstruct airflow.

At Bloomfield Cooling, Heating & Electric, our certified HVAC technicians will do a thorough system check during your routine annual maintenance calls. This helps avoid the issues noted above, proactively. They are also trained to diagnosis and repair problems with your furnace, boiler, or central air conditioner. Call us at 973-237-0505 if your furnace is blowing cold or cool air, if a heating emergency arises (we fix forced hot air furnaces, and steam or hot water boilers), and for your semi-annual routine maintenance.


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