Centrail A/C: Fan-only mode - can I control the fan speed?

Hi All,
I have central air conditioning, and in the summer I use it mainly in fan-only mode with a filter (for my wife's allergies). I can't seem to figure out how to turn down the fan speed. Sometimes it seems really fast, others not so fast, although maybe this is just in my imagination. Anyway, is there a way to control the fan speed? On the box it says the fan is variable speed. (Oldish style thermostat has just on/off.)
Thanks
Dean
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With out explicit information there is no way for anyone to help you. Most residential air handlers are set up to run in a given program, not manually other than off-on.
I suggest that you seek professional help locally and or the manufacture of the equipment.
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Its a TRANE heat pump, not sure if that also means the fan is also TRANE.
What makes the fan speed up or slow down when on fan-only mode?
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I can not see the unit from here. Trane makes 30 or so models of vfd's.
The Trane VFD I had included 4 programs that were changed by dip switches on the control board. I suggest you read your manual for YOUR UNIT completely. Then ask some questions.
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With Trane heat pumps, when the fan switch is set to ON at the thermostat, the fan (House Blower) normally runs at 50% air flow. If the compressor comes on, the blower will speed up to 100% after a delay, usually 1/2 to 8 1/2 minutes, depending on the program. The air flow is set by dip switches on the control board. It should then be verified by measuring with a flow hood.
Stretch
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