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thezeeman · Oct 29, 2008, 06:50 PM

Hello there,

Looking for some advice/information. I have a really old furnace (date found was 1949) :) Amazingly, this thing was working until now. I am planning on replacing it, but not until next year. I have no experience with HVAC at all, so the past couple of weeks I have been learning. In the summer when I set the thermostat to off, the blower still runs at intervals, this past summer it was starting to run but randomly would just buzz. I wasn't sure what was going on so I started to investigate.

Next thing that happened was it got to a point where all it would do is buzz. So I switched the breaker off so the fan wouldn't run and left the furnace off until I got a furnace guy to come out. So he came out and told me to switch everything on, it all started working so now I'm really confused.

I ended up cleaning it out because there was tons of dust/lint and crap in there, no filter on this old bad boy. I used a shop vac and a pancake w/ air blower to clean it out.

So it's been working since then until today. Today I noticed a melting/burning smell when the furnace kicked on, after it went off, it hasn't come back on. So I went back to investigate and the motor turns (this is a belt driven system) and the squirrel cage spins as well. I turned off the breaker/heat again and waited a few hours and turned it back on (thinking it would reset it or whatever) and it still didn't come back on.

So I thought maybe the motor needed oil so I oiled it and that still didn't do nothing. Now the weird thing is, when you turn off the heat, the blower kicks on and it works normal. When I turn on the heat, the burner ignites and heats up but the fan never turns on and it makes the furnace really hot. Yet, when you turn the heat off, the blower kicks on and cools the unit down. It also has 2 dials (cover says Combination Limit and Fan Control) so I played with those but it didn't do anything either. I'm trying to get this thing working for this year, then its gone. Anyone have any ideas?

hvac1000 · Oct 29, 2008, 06:56 PM

Could be a defective fan and limit control.
BUT
It could be the motor (did you check it by applying 120 volts directly or jumping out the fan limit control?)

If the motor runs sometimes but not others it could be the motor or the control. Does the motor get hot to the touch?

thezeeman · Oct 29, 2008, 06:58 PM

No I don't know how to do that stuff :)

But the motor only gets hot when the burner kicks on and heats it up, when its running in off mode its not hot at all.

hvac1000 · Oct 29, 2008, 07:07 PM

If you cannot check things I understand. Best to call for ON SITE service before it gets to cold.

thezeeman · Oct 29, 2008, 07:09 PM

I just realized you're a real hVAC person :) In your opinion, would it be best to just get a new furnace or put $$$ into repairing this one.

If I get a new one, my neighbor said he'd help me (he installed his and his uncle is his heating guy, he just did a final inspection to make sure all was hooked up correctly) so I would be bypassing the labor charges.

This one is very inefficient, it's 80K BTU in/64K BTU out and my house is 1466 sq. ft, 2 story.

hvac1000 · Oct 29, 2008, 08:21 PM

The old furnace is a guaranteed gas hog so replacing it would actually pay you back on energy savings quickly. If you have the $$ I would replace it now instead of tossing $$$ at the old one.

thezeeman · Oct 29, 2008, 08:23 PM

Thanks for the reply, I think I will go that route. I am sick of trying to figure this ancient thing out :)