On this draft inducer bottom bearing is worn so blades are touching housing making noise

A whistling sound from the inducer fan of a gas furnace is often an indication of a problem with the fan, which could be due to several reasons such as:

1. Dirty or clogged fan blades: Over time, the fan blades can accumulate dirt, dust, or debris, which can impede the flow of air and cause a whistling sound. In this case, cleaning the blades can often solve the problem.
2. Worn out bearings: The bearings in the fan motor can wear out over time, which can cause the fan to make a whistling sound. If this is the case, the motor may need to be replaced.
3. Damaged or loose fan blades: If the fan blades are damaged or have become loose, they can cause the fan to vibrate and create a whistling sound. In this case, the blades may need to be repaired or replaced.
4. Improperly sized ductwork: If the ductwork is too small or improperly sized, it can cause air to flow through the system at a higher velocity, which can create a whistling sound.

It's recommended to call a professional HVAC technician to inspect and diagnose the issue with your furnace and perform any necessary repairs or replacements.

The induced draft motor has a induced draft proving switch that is a pressure switch , it resembles a silver round flat device about 4 inches across with 2 wires, it will have a tubing attached to it that also is attached to the induced draft assembly housing on a barbed port, this is how the induced draft is "proven" thus giving the A OK to go to the next sequence of operation which is ignition trial period, it will attempt a ignition sequence for about 30 seconds 3 times before it will lock out if it has a circuit board, if so a flashing code will be observed and the legend in the back side of the blower door will tell you the codes meaning.
What is wrong 80% of the time is the barbed port on the induced drafts assembly is obstructed by carbon and not allowing the pressure switch to "sense" / prove the induced draft motor is running. You can connect the pressure switches 2 wires after the induced draft begins, this simulates a operational pressure switch and should begin the ignition phase if all is well, otherwise if all safety's or high limits are closed, then the ignition module is bad.

This is for spark type, if you have a hot surface ignitor look to se if its broken or cracked or has a burned spot visible, if not try testing for 120 volts to it, if you read proper voltage, then the hot surface igniter is bad.

Bad induction assembly is common with these units. If it's the style that has the motor install in what looks like a square black plastic box with tube connections off to the left and right. Replace the whole assembly, not just the motor. If you are mechanically inclined replacement isn't to hard.(make sure electricity to furnace is off). Cost to purchase induction assembly(look online) is around $300. If you have a company do it expect a bill between 650 and 800.

While you may be able to get just a motor it will not save you much. You will also run the risk of damage to the housing or fan(s) when you take the old one apart and try to install a new motor. Unless the new blower unit is several hundred dollars I would recommend you replace the whole assembly.

John

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Either you have moisture in the fan housing or the fan blade lost a counterweight. Pull off the lower hose going to your condensate drain and check for moisture. If you find none, you will need to replace the inducer fan assembly.

check for "stuff" inside the housing

Check the draft inducer motor for any partial blockages or dibri.

I've seen sticks, birds nest particles and pieces of deteriorating fan blades (squirrel cage type fans) cause this.

You might also find that the inducer motors bearing are going.

If its a loud vibrating grinding type noise, I'd suspect bearings or missing pieces of the blades. (unbalanced)
If it's a clanking type noise I'd suspect loose items hitting the fan.

The inducer motor will only operate right before and during burner operation, while the blower motor can operate at any time depending on your setting.