Just saw your post Marley and logged in ok.
I am not knowledgeable in electrics to be able to give sound investigation diagnosis or testing advice.
Does the fan work on cold blower ie when the dial is turned upwards (anti clockwise) ? If not provided the 12v power is on…….possibly a fuse ( better that than the fan motor) are all other 12v functions working normally as that might give a clue which/ where fuse.
We are just about packed ready for a short trip away so unable to read up or think of solutions at the moment.
Hope you find an easy solution