Hot Air Furnace Will Not Shut Off

 
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Old 02-08-2011, 04:01 PM   #1
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Hot Air Furnace Will Not Shut Off


Should not have got into it-but I did-Furnace in a dirt crawl space with no room to work. I was there for another "electrical" job & the customer said that she had a unit that the furnace would not shut off & it was over a hundred in the place.
First I unhooked the T-stat to no avail. Went in the crawl space & unhooked the wires from the T-stat-still running. Shut it off with the breaker.
Found the Honeywell Control circuit board with a couple of burnt resistors on it. Ok theres the problem. Went out & got a replacement board Honeywell ST9103A1002 & changed it out. The Blower fan starts first & 30 to 45 sec later the Burner...... Stat satisfied still won't shut down-unhooked stat wires again with same- Whats up?
Isn't the Blower supposed to start after the Burner? I checked my wiring over & over & everything seems right.. Any Thoughts ??? Thanks in Advance...........
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Old 02-08-2011, 08:57 PM   #2
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Re: Hot Air Furnace Will Not Shut Off


Does the blower stay on all the time or do the burners stay on all the time?

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Old 02-09-2011, 05:12 AM   #3
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Re: Hot Air Furnace Will Not Shut Off


Quote:
Originally Posted by flashheatingand View Post
Does the blower stay on all the time or do the burners stay on all the time?
Both stay on until I cut the power........I have to figure out why the limits don't open up & shut it down.. Any ideas?
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Old 02-09-2011, 08:08 AM   #4
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Re: Hot Air Furnace Will Not Shut Off


The limits shut it down if the furnace overheats, its not a bad thing if the furnace can run indefinitely.
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Old 02-09-2011, 08:12 AM   #5
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Re: Hot Air Furnace Will Not Shut Off


But clearly somehow something is wired wrong. There should be a wiring diagram on the back of one of the panels. I wish I could be of more help, but it sounds like something one has to be present.
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Old 02-09-2011, 11:29 AM   #6
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Re: Hot Air Furnace Will Not Shut Off


theres a relay thats sticking
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Old 02-13-2011, 02:41 PM   #7
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Re: Hot Air Furnace Will Not Shut Off


Disconnect stat wires at furnace to eliminate field installed control. If problem persists, you know it is in the furnace control. (I.E. stuck relay.)
May be a shorted stat wire.
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Old 02-23-2011, 06:36 PM   #8
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Re: Hot Air Furnace Will Not Shut Off


make? model? Fuel type?

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