Steve,
You are hearing this fan noise from outside of the coach, near the passenger steer tire?
What you might be hearing is the condenser fan for the dash AC. The condenser and fan are located high and aft of the front axle. You should be able to see the condenser by looking between the wheel well and passenger steer tire at about the 11 o’clock position. The fan will run ANYTIME the ignition key is in the acc OR run position and the heat selector is turned to any of the AC positions (left of the off position) or the two defrost positions (right of the off position). It should not run if the ignition key is off, or the heat selector is not set to AC or defrost. If the noise that you’re hearing is the condenser fan, and it runs all of the time you probably have a stuck relay.
I know these coaches are like snowflakes, but the HWH aux compressor on a 2006 Patriot or Marquis should be located passenger side, above and just forward of the drive axle. You should be able to see the compressor by looking between the wheel well and top of the passenger tire at about the 1 o’clock position (the coach may need to be raised slightly).
-Scott