My home is heated by a Bryant 359AAV furnace. The thermostat controls and indicates whether the fan is ON or OFF, but the furnace has a four-speed fan. I believe the installer set the fan on "HI" and I would like to turn it down both for quiet and electricity savings. Given the external static pressure, "MED-HI" would still move enough air, and "MED-LO" is only a little out of spec.
I obtained the user's manual and fan speed adjustment is not covered. Then I inspected the furnace circuit board but couldn't tell where the adjustment happens. Then I had two phone conversations with Bryant customer service, who deliberately would not tell me jumper or switch controls the fan speed, ostensibly because of implications for my warranty (I'm not sure if I have one). They want me to call the original installer, or refer another professional.
How can I adjust the fan speed?
Edit: a helpful user found the more technical service manual, which does address the wire colors for each speed.