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Old 10-27-2008, 03:54 PM   #1
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york funace intermittent start

Have a york high efficiecy 2 yrs old,vent motor starts but keeps shutting down ,ignitor won't light.If you pull the tube from the firebox thats connected to the pressure switch furnace starts up.Checked vents drains everything clear and filter .Leads me too believe pressure switch faulty.But when I suck on tube from pressure switch there is continuity across contacts.Diagnostics also indicate pressure switch.Could it be something else? thanks


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Old 10-27-2008, 05:41 PM   #2
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From what you describe, it sounds most likely like a bad pressure switch, but look for a clog or debris at the port the hose plugs onto at the 'firebox'. Also check for plugs/clogs in the exhaust pipe, and intake pipe if applicable, and that the condensate drain isn't plugged, just to be sure.

Most of the time, you can suck on the pressure switch and it will close. Problem is that the switch is very sensitive to pressure differences, and can only really be checked with the proper gauge. Most switches activate around one inch of water column or less (some slightly more). If I remember right, 28 inches of water column is equal to about one pound of pressure. So you can see, 1 inch is a very small amount of pressure.



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Old 10-28-2008, 07:29 AM   #3
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Could be a cracked trap.
Could be a restricted secondary heat exchanger if its LP.

Need to find out why the switch is not sensing enough pressure differential.
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Old 10-30-2008, 08:14 PM   #4
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Thanks, checked all ports and cleaned all hose .Furnace seems too be working fine now.
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