2014 cascadia Fan blower behind driver seat always on

I’m driving a 2014 Cascadia evolution,
I have a tripac APU, between the driver seat and the bunk there is a fan blower below the desk/storage that comes on when cab a/c/heat or APU in use.
Problem now that fan blower stays on all the time to stop it I have to turn off the battery switch on driver side door.
Anyone had similar issue or fix?

 

I called the dealer they said that the fan needs to be replaced because there is a short inside.
I’ll be saying my prayers on the way to the dealer for the cost to be low.

 

Before my trip to the dealer I did some research
it’s the Sleeper HVAC - blower fan housing there is an air filter there that needs to be change
See: owner manual page 83, 83/3
I will try to change the filter first.