First, we need to determine what part of the furnace is not shutting off… is it the blower fan that’s blowing continuously or are the gas furnace burners or electric heat strips in an Electric Furnace known as an Air Handler Unit (AHU) not cycling off?
Since these are two separate issues, we’ll address them separately:
1) The Blower Fan: the blower fan’s function is to push the air (heated or not) through the duct system. In normal operation, the fan should be turning off as the gas burners or electric heat strips cycle. If it is not shutting off, a common cause may be as simple as checking to see if the thermostat fan setting is on AUTO. If not, switch it from On to Auto. If this does not solve the issue, it could be the thermostat or control related.
If cool/cold air is blowing out, first check the air filter; a dirty furnace filter is one of the biggest causes for a furnace to continuously run or “short cycle”. It restricts airflow across the heat exchanger which causes it to get too hot then the furnace goes into the cool down mode, will run the fan continuously and will cause your furnace to blow cold air. When the AHU heat strips are not coming or the gas furnace pilot light won’t light or stay lit, may be control related.
When to call for a Service Technician to diagnose the problem: If it won’t light or it keeps going out, or the AHU heating strips are not generating heat
2) Heat Won’t Shut Off: when hot air continues to blow through the registers and the temperature rises past the thermostat setting, the furnace burners or electric heat strips are not turning off. Check the thermostat by turning it lowering the temperature setting to see if furnace or AHU shuts off. If not, the thermostat batteries may need replaced. If changing batteries did not solve the issue, it could be time to call a HVAC service technician to diagnose and repair your furnace correctly.
There are many reasons your furnace could be running more than usual and most of the causes fall back to regular maintenance. Proper HVAC maintenance is necessary to keep the HVAC equipment tuned and running efficient and will also help cut energy costs to save you money. Unfortunately, even with proper maintenance, as the heating and cooling equipment age and the demands of constant use, sometimes there are unexpected and unwelcomed failures.
Our goal is to help you get the most out of your existing equipment before furnace replacement is inevitable. If you find yourself needing furnace repair services, contact the HVAC contractors at ABLE Heat & Cool 636-528-4794 or visit our website https://www.ableheatcool.biz
