Furnace blower does not shut off


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Old 12-19-11, 04:54 PM
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Furnace blower does not shut off



I have a BDP furnace model 394gaw036075. (circa early 80's) It functions fine, except the fan does not shut off when the house reaches temp. Even if you move the thermostat control to the off position the fan continues to run. If you disconnect the unit from power for several hours and plug it back in the fan immediately starts to run. If I tap on the upper right hand corner of the galvanized box shown in the upper middle of the picture the fan will shut off like it should. Someone has suggested that my problem may be that the 24 volt transformer may have failed. This makes no sense to me as i can not understand why tapping on the box would restore power from the transformer. It seems to me more like a stuck switch, but I have no clue about such things. Thanks for your help in advance. I would really like to fix this myself and avoid having to hire someone, especially this close to christmas....

http://img585.imageshack.us/img585/3594/photoibk.jpg
 

Last edited by chad B; 12-19-11 at 05:00 PM. Reason: link to picture missing
  #2  
Old 12-19-11, 05:11 PM
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If the transformer had gone bad the furnace would not operate at all. I agree it sounds like a sticking fan switch but I don't think there is one on that furnace. If you would, remove the cover from that galvanized box & post a picture or more of what's in there.
 
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Old 12-19-11, 08:58 PM
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The GAW furnace has a timer that controls the fan on the circuit board. The thermostat wires below that box are on the circuit board.

You have a bad circuit board that needs to be replaced.
 
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Old 12-23-11, 12:32 PM
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Furnace Blower does not turn off (pic of circuit board)

Grady, thanks for your help. Sorry for the delay i posting this. Christmas season has me scrambling. Thanks again for your help.


chad
http://img829.imageshack.us/img829/8...rcuitboard.jpg
 
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Old 12-23-11, 01:10 PM
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Originally Posted by chad B
Grady, thanks for your help. Sorry for the delay i posting this. Christmas season has me scrambling. Thanks again for your help.


chad
http://img829.imageshack.us/img829/8...rcuitboard.jpg
As SP stated you need a new control board.
 
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Old 12-23-11, 02:07 PM
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Chad, Thank you but it was S/P who diagnosed the bad board.

Merry Christmas
 
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Old 12-23-11, 02:26 PM
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That is a really old circuit board. I'll bet you'd find the date code on it would show it was made about 1975.

Usually the date code gives the number of the week it was manufactured and the year---

WWYY or YYWW
 
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Old 12-23-11, 08:28 PM
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Originally Posted by Grady
Chad, Thank you but it was S/P who diagnosed the bad board.

Merry Christmas
Yeah, but I was going to tell S/P to tell him that
 
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Old 12-24-11, 08:24 AM
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Furnace Blower does not turn off

Thanks to SP and Grady for your help! Any ideas on were to start looking for a new circuit board for this? Will it be hard to find?


Chad
 
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Old 12-24-11, 08:55 AM
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Honeywell & White-Rodgers both make "universal" furnace control boards. I know Honeywell has a cross reference search engine on thier site. Not sure if White-Rodgers (Emerson) still does or not. The original board might still be available if you have a part #.
 
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Old 12-24-11, 09:02 AM
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Try here:
American HVAC Parts: Privacy Policy

shop around, I'm sure you can find a better price, I hope

Type in your furnace model and "furnace circuit board"

also: Carrier Bryant Payne Furnace Fan Control Board 302075-3 | eBay

furnace circuit boards - BuyCheapr.com
 
 

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