The aux fan "appears" or actually really is running?? Important difference right?

CMIIW, but if you're driving with cold air and you pull over immediately, the aux fan should be running low speed. Later, if you're not moving and the air is now outside air temp, also look to see if the aux fan is running- it should be.

Or, jump the aux fan to check that it is functional, to rule out if it is the or part of the problem.

There are indie shops that can work on it as well.