Q. Is it better to run the roof air conditioning or the dash air while
traveling in a motorhome?
A. When you are driving, the engine has to run
anyway; so, use the dash air. If you run the roof air, you also have to run the generator,
which puts extra wear and tear on that and increases fuel use. Place a sheet of clear
plastic between the driver’s compartment and the interior to keep the cab cool and reduce
the load on the dash air.