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S Jacobsen · Dec 27, 2008, 07:53 AM

I have a York Diamond 80 furnace Model# P4HUAR12N03201A. New construction 05 installation. Went away from this house for 2 months. Came back and furnace won't operate. System ignites, heats up plenum, blower comes on, and then the fire immediately goes out. Has a component failed or has the 2 month downtime created a different issue?

KC13 · Dec 27, 2008, 08:00 AM

Look for a diagnostic LED through a clear plug in one of the front panels. Is it flashing? Observe the pattern/number of flashes and compare to service label - usually found on one of the panels or on the furnace control board. Post results.

S Jacobsen · Dec 27, 2008, 08:38 AM

Originally Posted by KC13

Look for a diagnostic LED through a clear plug in one of the front panels. Is it flashing? Observe the pattern/number of flashes and compare to service label - usually found on one of the panels or on the furnace control board. Post results.

No flashing.

KC13 · Dec 27, 2008, 08:44 AM

I should have mentioned, check with furnace running. If short-cycle repeats but no LED code is displayed, the thermostat may be the problem. Bypassing the R-W circuit will allow you to check this.

S Jacobsen · Dec 27, 2008, 09:34 AM

Originally Posted by KC13

Look for a diagnostic LED through a clear plug in one of the front panels. Is it flashing? Observe the pattern/number of flashes and compare to service label - usually found on one of the panels or on the furnace control board. Post results.

No flashing.

MarkwithaK · Dec 27, 2008, 09:49 AM

Did the system function normally before you left? Was it idle the entire 2 months?

S Jacobsen · Dec 27, 2008, 09:58 AM

Originally Posted by KC13

I should have mentioned, check with furnace running. If short-cycle repeats but no LED code is displayed, the thermostat may be the problem. Bypassing the R-W circuit will allow you to check this.

Thank you very much. The furnace is running with a jumper on the R-W circuit in place. Although the furnace does not run continuously. It runs for a few minutes and then shuts down for a few minutes and then restarts again.

S Jacobsen · Dec 27, 2008, 10:00 AM

Originally Posted by MarkwithaK

Did the system function normally before you left? Was it idle the entire 2 months?

Yes. AC worked. Heat has not been used since last March or April and then it worked fine.

MarkwithaK · Dec 27, 2008, 10:01 AM

If you jumped R-W and you are still getting the short cycling then your stat isn't the problem. What condition is your filter in? You could be bouncing off the high limit switch.

S Jacobsen · Dec 27, 2008, 11:10 AM

Originally Posted by MarkwithaK

If you jumped R-W and you are still getting the short cycling then your stat isn't the problem. What condition is your filter in? You could be bouncing off of the high limit switch.

Filter is new.

KC13 · Dec 27, 2008, 11:18 AM

Still no LED flashing?

MarkwithaK · Dec 27, 2008, 12:04 PM

I'm still leaning towards the high limit. Hard to pin it down without actually being there. The coil could be plugged. I would be interested to know what the temperature rise is.

S Jacobsen · Dec 27, 2008, 06:54 PM

Originally Posted by S Jacobsen

Filter is new.

FYI Solution found: Burner forced draft system had small particles of debris. Upon furnace restart one small particle partially plugged vacuum hose leading to the safety switch. Blowing out the debris allowed air draft hose connected to the switch to clear and the switch began to function again.