Ultra SX 80 exhaust fan cycles over and over? - http://www.hvacmechanic.com/ Forums
Original message
| TimB
 |  "Ultra SX 80 exhaust fan cycles over and over?"
, posted Sat 23 Oct 15:04:  
We have an Armstrong Ultra SX 80 furnace.
The furnace runs fine when heating...but when it is not heating the exhaust fan turns on and runs for about 5 seconds then shuts off and turns on again, over and over. The exhaust fan The problem started on its own...same programmable thermostat,no one has serviced it lately. I vacuumed it out and could see nothing visually wrong. Any idea what might be the problem? Thanks.
[this message was edited by TimB on Sun 24 Oct 12:46] |
| Replies:
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| xenos
Webmaster 
| "Re(1):Ultra SX 80 exhaust fan cycles over and" , posted Sat 23 Oct 19:30
With this discription almost anything.
Xenos.
The best way to escape a problem is to solve it.
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| | Freon
| "Re(2):Ultra SX 80 exhaust fan cycles over and" , posted Sun 24 Oct 14:57
You might check the setting of the low temperature blower turn-off switch. Possibly it's set just low enough to cause this type of oscillation. If your furnace is old, this switch is most likely in a 3X5 aluminum box near to the control box but toward the end of the furnace where the air exits. Remove the cover and you'll see a dial and 3 sliders. The low temp slider should be the one positioned most clockwise-- at the low end of the temperature scale on the circular dial.
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