air handler noise

For the last month or so I've noticed a low rythmic rumbling noise coming from one of my Trane air handlers. Its similar to the rumbling noise heard accasionally from a kitchen refrigerator. The air handler is original (18 years old) Its outside heat pump was replaced last April. The rumbling can be heard at the room air registers. It is not loud and
barely noticeable but I was wondering if this is normal. The air filters are maintained monthly. Thanks for your help
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If it never did it before, it is not normal.
Check the motor and blower bearings. Could be they are starting to go and causing some reverberation.
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Edwin Pawlowski wrote:

When I heard a noise like that from one of my Trane air handlers when it was about 10 years old I found that the blower wheel had developed a fatigue crack about 2/3 of the way around it's fastening hub and was vibrating. It probably would have fallen completely off in a few more days of running like that.
A new blower wheel and a some hands on work put things right again.
It would have been a heck of a lot easier for me to do that job the AHs who installed the system hadn't routed the refrigeration tubing right across the front of the unit so I couldn't slide the blower assembly out (as designed) to service it.
I had to squeeze in a sabre saw and cut off a bit of one bracket and then juggle the motor and blower wheel while they were still inside the unit to get that job done. I felt like I was a dentist trying to fill a tooth by accessing it through the patient's rectum, but it was preferable to having to pay a tech to suck out the refrigerant, reroute the lines and recharge the system.
Five seconds of foresight by the original installers about where to route the refrigerant lines would have made that job a snap. Shoosh! (End of rant.)
--
Jeffry Wisnia

(W1BSV + Brass Rat \'57 EE)
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On Sat, 12 Nov 2005 11:06:38 -0500, Jeff Wisnia

What i really hate when trying to get a blower out are furnaces that have the damn flue in front of the blower. I'd like to slap the asshole that came up with that brilliant idea.
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Something is wrong.
Check for a restricted (dirty) indoor coil . Also look for bad motor bearings. Also check for a dirty blower wheel.
By the way, you SHOULD replace the indoor unit when you replace the outdoor unit. They are made as matched sets and should be replaced together. What you did is sort of like putting a Ford transmission in a Chevy. It may work but not as efficiently as is possible.
Stretch
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