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.
Best Answer
When you look at the motor there are 7 wires. 2 brown for the capacitor, a White common wire, Black for high, orange for medium high, blue for medium low and red for low. It comes from the factory with the black plugged into cool and the orange plugged into heat. Blue and red are hooked to M1 and M2 which are just place holders. To reduce speed swap the orange wire with either the blue or red wires on the circuit board. I have to warn you however that low air flow can damage the furnace and actually be less efficient. You should take the temperature at the outlet of the furnace and at the inlet of the furnace. Subtract the two, this will give you your split. Compare that to the required split on the nameplate of the furnace. If it is too high you need more air. I have seen cases where the furnace is too large for the ducts and was overheating even on high speed.