The fan clutch does not engage if it cannot sense the heat blowing over it thru the radiator ,so Neal is right about making sure your radiator fins and the core itself are clean ,if you core is partially blocked it cannot get rid of the heat .Make sure your getting the big heavy duty fan clutch ,it will be listed in the parts book for motorhomes ,not just a heavy duty pickup .most will engage at 180 to 210 degrees ,some are more sensative ,you'll hear it come on loud and clear .also ,when cold ,starting up your coach ,youll hear the fan
roar loudy for a few minutes idling or driving ,then it will disengage to the
normal engine sound until engine temperatures go up hotter .Make sure your
going with a quality part ,they are not all the same ,try checking out Napa
brands or even carquest auto parts .The beefy unit will be obviouse compared to the standard types .
Scott of scottanlily