How to Adjust Blower Belt Tension on a Forced Air Furnace

What You'll Need
Wrench of the proper size
2 foot length of 2X4 board

You have a forced air furnace in your house. Every time it starts up it squeals badly. You know that in a car this signifies that a belt is loose and slipping. In a forced air system, squeaking signifies the same thing. If you’re hearing squeaking or squealing every time the furnace blower starts up, you will need to re-tension the belt that drives the blower fan. Below are the steps required to perform this operation and the tools you’ll need.

Step 1: Gain Access

Before you can tighten the belt, you need to remove the blower access panel to get to the belt and motor. On some furnaces this will require a Phillips screwdriver, while others may require a straight slot and still others may require a wrench or nut driver. Turn off the power at the breaker panel first.

Step 2: Check the Belt

Once you have access to the belt, you need to check its condition. If you see chunks missing or cracks, loosen the motor adjusting bolts and remove the belt. Take it to an auto parts store and have them match the belt to a new one. If the belt is in good shape, push down on it in the center between the pulleys. If you can move it more than one inch, you need to adjust it.

Step 3: Tighten the Belt

To tighten the belt, loosen the one or two motor adjusting screws and using the 2X4, pry the motor away from the blower pulley. Once the desired tension has been reached, tighten the bolts securely and replace the access cover.