Furnace High Pitched Squeal

Question

My furnace unit started making a squealing sound today. Does anyone know what this is? Anything I can fix myself?

Maybe related, the temp was high 90s today and the AC was actually behind. I have it set at 76 and it was at 78 early this afternoon and still hasn't shut off yet, 6 hours later. Secondary question, should it be behind or is that another issue?

It squeals for 2-3 minutes, then is silent for probably 2-3 minutes.

Video: https://youtu.be/yWVDllF5rrc

EDIT: Is this where the oil goes, this black tube?

Answer 1

If the blower in the furnace is belt driven (not likely), the belt might be worn and slipping. Most likely, the blower is direct drive, which means you'll probably have to pull out the entire blower assembly to get at the motor.

WARNING:

• Before removing the blower, make sure power to the unit is OFF.
• If you have to remove wiring to pull out the blower assembly, make sure you label each wire so you know where it goes.

Once you have the blower out and accessible, you should be able to locate the two oil ports. These ports are typically on the "top" of the motor, and are plugged with plastic or metal caps. Remove the caps, fill it up with oil, and replace the caps. Check the manufacturer's documentation for the type, and amount of oil to use.

Here's a good YouTube video from Grayfurnaceman that shows How to oil the HVAC fan motor.

If the motor in your unit does not have oil ports, you might have to replace the bearings, motor, or the entire blower assembly (depending on which unit you have).

As always, if you don't feel comfortable doing this type of work, please contact a local licensed HVAC technician.

Answer 2

I listened to the UTube,,, could not hear what you described. With a audible noise on the condensing / compressor unit, I have found the problem to be the bearings in the fan. Some 3/1 oil or WD40 in the bearings close to the motor shaft of the fan may help. If this helps the grease in the bearings has dried out and the oil may give a few more years of life. After this the bearings in the fan motor will need to be replaced / or the motor itself. Since you have an oil port a few drops of automotive oil would work well.