Squeaky Furnace

I started noticing a really bad squeaky sound coming from the furnace. It usually happens right away when it kicks on, then goes away after it has run for a while (but sometimes it will start at arbitrary times).
I assume I need to oil something but I'm not sure what and what type of oil to use.
Any suggestions?
Thanks, Dan
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Two possibilities:
1. Motor bearings need oil -- 10W30 motor oil will work. Use a pump oiler with a long spout to reach:
a. Bearings (2) on motor b. Bearings (2) on shaft ends of fan, if belt driven..
You may have to loosen things to pull the fan assembly out so you can get at it.
2. Slipping fan belt, if so equipped. There should be a tensioning screw or other adjustment. Set so firm thumb pressure depresses belt about 1/2" It also sometimes helps to use "belt dressing" on the belt.
I keep a spare belt on hand at all times. Size is stamped on the top (outside) of the belt. Any good hardware or auto parts store.
Check belts and/or bearing twice a year. Check burning/pilot light at same time. I check at the beginning and the end of the heating season.
Do filters monthly. Consider a "washable" filter and spray-filter oil for better dust pickup.
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I see two fans in there.. One is smaller and is connected to the exhaust, and one is a larger squirrel cage.. Which one do I need to oil? Of course, now I can't get it to make noise again so I don't know exactly which one the noise is coming from.
The larger fan looks like it would be quite a chore to pull out.. There are various other boxes mounted in front.
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On Sat, 19 Jan 2008 14:05:32 -0800 (PST), lagman

You would need to oil the motor that is squeaking but the high efficiency furnace you have most likely does not have oil ports. Usually a squeaking noise is caused by a pending bearing failure which results in a motor failure. Nothing you can do about it unless the squeak is something else. Bubba
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It started squeaking again. This time I took off the cover and was able to confirm that the sound is coming from the smaller fan attached to the exhaust. This makes me worried.. If this motor fails, will I have a basement full of CO2?
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On Sat, 19 Jan 2008 22:27:43 -0800 (PST), lagman

Well, I have good news and bad news. The bad news is, your home is already full of CO2. The good news is, you home is already full of CO2. Luckily your home is NOT full of CO. If the inducer quits, the pressure switch will sense this and shut off the burner. Get the motor replaced. Bubba
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Use machine oil and take the time to turn the power off least the fan start or the furnace then follow the rest
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wrote:

Hey junior Jim, In case you havent been around the last 20+ years or so, ..........................Inducer motors dont have oil ports. You get a built in "xx" amount of hours out of them and then you replace them. Bubba
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wrote:

I thought you'd come up with a howler like that. You can probably take the OP for an extrra $100 on you call for saving him from a fate worse than death.
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On Sat, 19 Jan 2008 22:27:43 -0800 (PST), lagman

Go to a HVAC supplies shop and get a new fan. Replace. Its not worth the time and effort to fool around fixing it.
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The larger one is typically the noisy one.
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Christopher A. Young
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Oh, gosh, don't use 10W30. That absorbs moisture from the air. Please, don't use detergent oils.
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On Jan 20, 1:30 am, "Stormin Mormon"

Huh? What about a car engine then?? I have never had anything that I could attribute to moisture absorbtion in oil. A citation, please...
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Car engine gets hot enough to drive the moisture out. Common knowledge among techs. Here is your citaton:
"Heating techs have known for many years not to use detergent oils for electric motors. The detergent oils absorb moisture from the air. The oil then foams up, rusts iron or steel berrings, and loses lubrcity. Electric motors do not get hot enough to drive the moisture out of detergent oils." C.A.Young, 2008.
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My old clunker had oil cups on the blower and oil ports on the motor, newer stuff is sealed bearings you cant oil. Maybe a loose belt. I think any oil is good, except cooking oil, although once as a kid I put mazola in the mower. Oil if you can but sound going away sounds like a belt if you have one.
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once as a kid I put mazola in the mower.
That was pretty corney.....
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You have to get up oily in the morning to fool Hardcrab.
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Fan motor berrings. ND-20 typically.
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On Sat, 19 Jan 2008 11:26:57 -0800 (PST), lagman

Stand by the furnace until it starts and figure out the source of the noise. If its the motor 10/30 motor oil on the motor bearings should work. A car's engine runs a lot hotter than you furnace so it will work.
If not and you have an old style gas furnace with a squirrel cage blower the bronze bearings are probably shot. They are quite easy to remove and to replace. A HVAC supplies shop will have replacements. They should cost less than $20. Check the cage shaft too to see any scouring. Replace the shaft or shift it sideways to present a good round shaft surface to the bearings if that is possible. The shaft and bearings are meant to run dry. Grease will dry up in the heat and cause problems. Oil will create an abrasive slurry with the bronze bearing shavings. Even if the bearings are not the problem $20 is a very cheap investment and resets the condition of your bearings for another 20 years of trouble free running.
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The squeaking we get here was actually the blower body vibrating on the bolts that held it in. Put a hand on it, it'd stop. A little oil around the screws & it stopped. Comes back abt every three years or so; pull dust off, oil again.
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