The fan is only supposed to come on if the unit gets too warm, so if you have it where it gets some air at each end that should be ok.
You are way better off with the LK for ever seeing the 14.6v that your battery needs at times. The LK will always start at 14.6 and do 30 minutes before dropping to 13.6v when in three-stage mode.
You likely have the unit installed where you can't get at it easily and from what you said before, you want to leave it in three-stage mode. It should be in that mode on arrival with the switch behind the left hand hole over to the left.
The pot behind the right hand hole should be left alone and should already be set for the correct three-stage voltages. If not, you can fix that, --see how to operate it here, para 10. (You need a flashlight and small screwdriver and a voltmeter in the output to see the voltage as you do the pot adjustment)
For accurate voltage "tuning" the unit must not be connected to the battery, or else the battery's lower voltage will drag down the voltage you see where the two try to "middle" their voltages. In real life, you can still twiddle the converter voltage up or down to change whatever voltage things are at now, but you won't be doing that probably.
If you ever get a different battery bank, you will appreciate having the LK which can be adjusted to meet any of the various battery charging specs.
https://powermaxconverters.com/wp-content/uploads/2018/05/PM3-12V-LK-Manual-2018.pdf
1. 1991 Oakland 28DB Class C
on Ford E350-460-7.5 Gas EFI
Photo in Profile
2. 1991 Bighorn 9.5ft Truck Camper on 2003 Chev 2500HD 6.0 Gas
See Profile for Electronic set-ups for 1. and 2.