Air Blower Cycles

Old 09-30-03, 05:52 PM
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Air Blower Cycles

I have a Trane XB80 Air Handler/Furnace recently I noticed my Air Blower was cycling along with air conditioning condenser outside. At first I suspected a thermostat problem a White Rogers 1F56W-444 mechanical heating/cooling type. I took the cover off and set the thermostat to constantly to call for cool. Both the blower and condenser would turn on for about 10 seconds and turn off for about 30 seconds and the cycle would repeat again. I then set the thermostat to OFF mode and put the Fan switch to ON from AUTO. As it should be condenser did not turn on and only the Blower came ON but it still continued to cycle as in previous step. At this point I could only suspect that the Integrated Fan Control Module (White Rogers 50A55-438) was the problem that was causing this. The diagnostic LED was blinking at proper rate indicating no problems but having a previous experience on another unit in the same house I found that this is not a good indicator of a problem with this unit. So I decided to replaced it with a new one but the problem still continues are there any additional interlocks to the Integrated Fan Control Module that could be causing this?? I have not tried this in the Heat mode (it still hot here in Texas) but I suspect that this will react the same way. Any thoughts??
Old 10-13-03, 12:00 AM
lynn comstock
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I guess that nobody has a clue on your problem. A knowledgeable tech should be able to figure it out with the right tools and a wiring diagram.
Old 10-13-03, 05:42 AM
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There isn't quite enough info to get a full picture. You say the blower and outdoor unit cycle. That is what they should do. Maybe not at that fast rate but in order to decide why they cycle too fast it would be helpful to know the indoor temp and setpoint of the thermostat. Does it cycle with the thermostat set to heat or off?
Old 10-13-03, 10:48 AM
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I would remove the t-stat off w/ power off.. undo the wire, and tie Red, Green, and Yellow together, turn on the power, and see what happens.. If the units stays on the whole time, then it's the t-stat..

make sure you don't have any air blowing right on the t-stat

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