If the temperatures are far apart, it will only run on hi fan. Adjust the Tstat temperature only a couple degrees above the room temperature since you are currently trying to heat your rig. Did this slow the fan down? If not, Try a system reset...with the Tstst turned Off, press the zone and mode buttons at the same time. IniT should display and then less the on/off button. Does it now control the fan speed? If not then the dip switches on the control board are not set properly.
Where in Bโville are you?
This post is my opinion (free advice). It is not intended to influence anyone's judgment nor do I advocate anyone do what I propose.
Sold 04 Dynasty to our son after 14 great years.
Upgraded with a 08 HR Navigator 45โ...