What could cause hot air to blow when air conditioner is on for a 2013 Nissan Altima?
First, you could have a defect in the AC system. Have that checked to make sure it's working properly. If it's not the AC itself, in the ductwork there's a blend door that throttles between hot/cold. Yours is probably sticking because the door actuator is defective. You may have noticed a tapping sound under the dash from a defective actuator. Try a spray lubricant on the actuator, or remove it to see if there's a broken sprocket. Might need replacing. It's not a difficult fix.
Where is the actuator located? I am hoping the compressor hasn't gone out. I am willing to try anything, just had to put a new transmission in it.
I did notice a little ticking noise before this happened.
Under the dashboard you'll see the HVAC ducts and the blend door actuators look like small boxes; I believe you have three. Operate the climate change and you'll be able to hear them operating. Again, before you start working on this, have your AC checked to make sure it's not just the AC that needs coolant or maybe just a fuse.
Which fuse could it possibly be? I looked at the fuse box and only saw 2 for the blower motor.
Would that also keep the compressor from engaging?
There's a fuse for the AC unit. don't know which one, but there should be a map to the fuses inside the box cover.