This is a generalization.
If the a/c is just OK, but not up to par and the temp gage is running a little high, check this:
If the sight glass looks decent[almost clear] , check for aux fan turning on. If you are slightly low on freon, the fan will not come on because it is activated by the high side pressure switch at the drier/reciever. If the fan runs when jumpered at this sw., then the fan circuit [relay,fuse, etc.] are ok. So , we have a bad switch/or too low trip pressure.[ possible low freon].
Both these will result in poor cooling. And the aux fan not coming on will also add to the high temp on the cabin gage. [ no air flow through a/c condenser and Radiator.]
Don't confuse the a/c condenser fan with the aux fan that comes on at extreme coolant temps, for that is another circuit. [ usually at a higher speed].
That fan will come on without a/c controls being on and its function is controling engine coolant temps.