How to Access the Main Blower in a Furnace

Design

• Furnaces are designed to have one of three different configurations that affect the direction in which they put out heat. An upflow furnace takes cool air in at the bottom of the furnace and puts warm air out from the top. You can usually find them in basements. Downflow furnaces, which are usually in attics, do the opposite, taking in cool air from the top and emitting it from the bottom. Furnaces with a horizontal or cross-flow configuration pull air in one side and discharge it out the other. A horizontal furnace is designed for limited spaces and lies on its side. Look for the furnace blower at the return air end of your heating system where the air is cooler.

Access

• Access to the blower compartment will be at the top, bottom or side section of the furnace depending on your furnace’s configuration. Before you can access the blower compartment, you’ll need to remove the main furnace door. When you do so, you’ll see the panel to the blower compartment. Remove it to access the main blower. When you do so, a safety switch should activate, which will disable the blower by turning off the furnace.

Safety Switch

• Older furnaces may not have a safety interlock switch. To protect yourself from injury, you should turn off power to the furnace before opening the blower compartment. Otherwise, you risk serious injury, including loss of fingers, if the blower fan, the drive motor or the belt are still operating when you reach inside the cabinet. Dangerous fumes can also leak out if you operate your furnace when the door to the blower compartment is open.

Re-installing

• When re-installing the doors on an upflow furnace, make sure the bottom door goes over the furnace frame, or the safety switch won’t engage and the furnace won’t run. On a downflow furnace, you need to ensure that the top door goes over the furnace frame.

LED

• Some furnaces have an LED status code display that provides information that is helpful while troubleshooting. If your furnace is displaying an LED status code, record the code before you remove the blower access door or turn off power to the furnace because the code will be erased from the control’s memory when you remove the door or turn off power.