On my 2002 Kia Sedona the switch that you turn to get the heat/ac to come on has 5 levels. When I turn in on, levels 1,2,4 and 5 work, but when I put it on 3 no air comes out. What might cause that issue? Also the lighting to illuminate that switch doesn’t work, all my other things control temp adn rear heat/air are lit and work.
You could have a bad contact on the switch, a broken wire, or (most likely) a burnt out element in the blower resistor pack.
The switch not being lit is another issue. It is most likely that the bulb behind the switch is burnt out, some fail sooner than others.
okay how tough is it to repair?
Fan speeds other than high are controlled by using a resistor to slow down the fan. You just burned out #3. You can replace the one resistor, the resistor pack or the whole assembly. Which is best depends on the car. Some are easy to get to some difficult.
The light is a different problem and you need to track the electrical fault.
Good Luck