PaPaPeng wrote:
On Sat, 19 Jan 2008 11:26:57 -0800 (PST), lagman
wrote:

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

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.

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.