How to Fix a Belt Blower on a Furnace

If your furnace is producing heat and otherwise working correctly, but has an intermittent or consistent squeal while it's running, it's likely that the rubber belt that drives the blower is slipping as it turns. This can happen as the belt ages. Generally, furnace issues should be handled by professionals, but this one is actually simple enough that any competent homeowner can do it. You should first try to stop the slippage by applying ``belt dressing,'' a sticky substance in a spray can that you can buy at any hardware store. If that doesn't work, you can replace the belt fairly easily.

Things You'll Need

• One piece of light-colored chalk One can of belt dressing

Instructions

Fixing the Belt

1. Turn off your furnace at the fuse box. Crank up the thermostat as a test, to make sure it's not going to kick on while you're working on it.

2. Open the access panel to the furnace and locate the belt-driven motor inside. It should be easily found. The belt will be a thin black or gray rubber line that is stretched in an elongated circle between the motor and the blower.

3. Find a spot where the belt is away from the motor and blower so that you can see the back of the belt (the part of the belt that comes in contact with the pulley on the motor). With your chalk, put a mark there, on the back of the belt.

4. Position your can of belt dressing so that the nozzle is pointing at the same spot on the back of the belt. Spray the belt dressing onto the back of the belt while slowly pulling the belt along with your free hand, until the chalk like that you've marked comes back around.

5. Close the access panel, turn the furnace back on and test for the squealing noise. If it's still doing it, then the belt will likely have to be replaced. Do this by releasing the pulley (the method varies between furnace models; check your owner's manual, or search online) to remove the belt, then take it to your local hardware store to get the correct replacement.

Tips & Warnings

• If your furnace has an on-off switch, turn it off while working on it, but also cut power at the fuse box. Make sure to test with the thermostat to confirm that it's off.

References

• More information available here.