furnace cycles, runs for 45-60 seconds shuts down and recycles again

ronsmoneypit · 02-02-2008, 06:17 PM

Hello all,
Please forgive me if I use the wrong terminology below, HVAC work is all new to me, I am a computer guy....

I have a comfortmaker furnace that is about 4 years old.
I just had the squirrelcage (blower motor wheel) changed last Monday because the original one separated at the weld and shook like crazy.

Today when I came home from work, I was told we had no heat.
The draft motor spins up, ignitor glows hot, the gas will then flow and the 4 flames are a bright blue. The blower motor kicks in, and after about 45-60 seconds, the furnace will shut down. It will then keep trying to go through this cycle and never stays lit.
The led for the smart valve is a steady flashing light which indicates normal operation. I do not see any pinched wires or strained connections.

Here is where it gets weird.
If I remove the top panel of the furnace (The one that covers the ignitor, draft fan, and gas lines) the furnace seems to work fine.

Can someone please point me in the right direction? I have been out of work for 6 months and do not have the cash right now to pay a pro to fix it. I know that the top panel should be in place but if I leave it off until I find steady work will I damage anything?? I do not think it will damage anything because it only has louvers that allow air into the furnace.
I have a carbon monoxide detector in the basement so I think I am covered.

I am stumped on this one.
Thank you in advance for your help.

Regards,
Ron

biggles · 02-02-2008, 08:19 PM

leave it off and enjoy the warmth check for a loose connection in your warmer days check the conections on the gas valve...everything is negative in and around the burnerso no swet on CD

CHECK ALL THE GROUNDS IFYOUR LOOKING AT ELECTRONICS WITHIN THE COVER THAT WAS REMOVED

ronsmoneypit · 02-03-2008, 08:10 AM

Hello Biggles,
Thanks for the quick reply.
I figured I would let it be until it warms up around here. I am in NJ so it will be a bit until it stays warm enough to be without heat. There does not seem to be any loose groundwires under the cover I will check under the bottom cover along the circuit board when things warm up.
In your reply what did you mean when you said "on CD

CHECK ALL THE GROUNDS IFYOUR LOOKING AT ELECTRONICS WITHIN THE COVER THAT WAS REMOVED"

Does CD mean cold day?

Thanks again,
Ron

biggles · 02-03-2008, 10:29 AM

sorry i meant CM as carbon monoxide..your induced draft motor pressurizes the gas inlets to mix and any burnt gas is the by product called CM isn't a worry item....GO GIANTS

if the unit was working before the blower was done and payment was check written you have a right to call for a call back to find the problem...the work ticket should give a grace on the repair,and state in writing that unit was left heating or cycled heating after repair.

52Caddy · 02-03-2008, 02:46 PM

Maybe an airflow problem across the heat exchanger, if there's not enough airflow perhaps it's kicking out on the high discharge temperature limit?

Are you sure the new blower fan is running the right direction? If I remember right a fan runs about 30% capacity when it's turning the wrong way.

That's what I'd look at since that was what was changed.