Atwood Furnace Squealing Noise

[geofferyh]

My Atwood 8535 IV furnace is making an intermittent squealing noise of varying pitch and amplitude, blower rotation actually seems quiet, it is more like a high pitched vibration as versus rotation noise. This high pitched squeal typically occurs shortly after the blower start running, or sometimes after it has run for awhile. The longer the blower is running the more likely the squealing is to stop. This is why I have pretty much eliminated blower motor rotation as the source. I can't see anything in the fan blades and I have a mud dubber screen on the exhaust.

Any ideas would be greatly appreciated before I start taking things apart.

[WSRG]

It's almost always the blower bearings that make the squealing noise that you are describing. It is possible to lube the bearings by removing the outside cover to expose the blower motor. The only way to lube them without having to disassemble the blower assembly, is to use a good quality squirt type oil [not WD-40] with a long tube to reach the bearings. Try not to get too much oil on the squirrel cage during this process.
Lubing the blower motor is only a temporary fix, since the squealing noise means that the bearings are already worn out. Hearing this noise almost always means that a blower motor replacement is in your future.

Bill

[geofferyh]

Quote:

Originally Posted by WSRG It's almost always the blower bearings that make the squealing noise that you are describing. It is possible to lube the bearings by removing the outside cover to expose the blower motor. The only way to lube them without having to disassemble the blower assembly, is to use a good quality squirt type oil [not WD-40] with a long tube to reach the bearings. Try not to get too much oil on the squirrel cage during this process. Lubing the blower motor is only a temporary fix, since the squealing noise means that the bearings are already worn out. Hearing this noise almost always means that a blower motor replacement is in your future. Bill

I'm not so sure about that Bill. Recall that the noise is more of a metalic vibration squeal rather than a rotating motor dry bearing rasping sound. A new development has now surfaced.

I have checked and found no obstructions or debris within the area of either cage fan. I removed the Draft Cap Assembly and found two metal pieces that look like parts of some kind of circular spring clip. See attachment.

[WSRG]

It's hard to make out what that part is. I don't have any reference to compare it's size. It may be a ring clip that goes around the hub of the combustion wheel to keep it tight on the motor shaft. It is also possible that it may be a part that was just left inside the furnace when the furnace was built or installed in your coach.

Let me know what you figure out.

Bill

[geofferyh]

I talked to the factory tech on the phone this afternoon. There is supposed to be a ring clip around the hub of the combustion wheel.

Mine is missing. Therefore, it is my belief that the metal pieces are what's left of the ring clip. It apparently broke off and made its way through the combustion chamber to the exhaust port. The wheel is still firmly in place. Should probably get another ring clip though.

I still think the squealing noise is vibration related, even though the Atwood Tech thinks I may have a motor bearing that is going bad. In that this is an intermittent problem, I don't see how it could be a motor bearing. I adjusted the Draft Cap Assembly for a tighter fit and better alignment. It has the only metal to metal fit in the combustion chamber area. I'll know more tonight when the furnace is in use again.

[WSRG]

Keep in mind that the bearings on the blower motor are bronze oillite bearings and not ball bearings. They can make all kinds of different noises, ranging from a squealing to a rumbling noise when they go bad.

Also, did you check to make sure that both the cumbustion wheel as well as the blower wheel are turning true inside both of their cages. Either of these wheels could be bent slightly...causing an out of balance condition that would put extra strain on the bearings.

Bill

[ksg5000]

Read hundreds of furnace squeal threads over the yrs and every one of them has been blower related.

The blower motor is easily accessible when you remove the exterior shield. You might consider starting up the furnace with the exterior shield lowered - probably hear/feel the squeal coming directly from the motor.

Replacing the motor on a 8500 series furnace isn't very hard and you don't have to removal the furnace.

[geofferyh]

You guys make good points.

Since the metal parts found are now known to be from the combustion side wheel hub ring clip, I was planning on checking the wheel alignment next. Also, since all the material associated with the broken ring clip has not been found as yet, I am going to blow HP air around and through the wheel vanes just in case that material might be associated with the squeal. I should be able to get any remaining debris to exit via the exhaust port.

[geofferyh]

I finally solved the "Squeal" problem and it was not a motor bearing. Hey, when was the last time I have seen a light duty motor with bronze bearings wear out with only maybe a years worth of run time. Duh, almost never. However, I suspect many motors have been replaced over what should have been a truly simple fix.

Remember, the metal retaining clip ring around the hub of the exhaust wheel cage fan broke. This allowed the wheel to migrate inward to begin minor contact with the plastic housing. Plastic housing + Plastic Wheel = "Squeal".

Moved the wheel back out about 1/32" and replaced the ring clip with one that I got from the NAPA Auto Parts store. (The RV supply store sells the clip, but only with a replacement wheel for $25!).

Hope this helps someone else.

[SpursMVP]

We seem to be having the same problem. It's not a squeal, but rather a rattle.

Took off the cover and observed/listened and the motor seems to be running very smoothly. Checked the retainer clip on the end of the shaft the wheel is on...it was on snuggly.

Are there any other parts that could rattle? I've checked all the screws and all are tight.

[Its Paid For]

I fixed same problem about 6 months ago. Wish I had read thread sooner, could have saved you time.