How do I trouble shoot an interor fan on a 2010 Dodge Caliber that is not blowing air?

It has a fuse and a relay. The relay is mostly for high speed. If the motor only works at high speed then I would say your heater resistor is bad. If does not work at all. It can still be heater resistor. What you need is a test light that draws amps. I use a old head light. Hook it up to the blower motor plug and turn the fan on with ignition on it light comes on the motor is mostly bad. If the light does not come on. Most likely the resistor is bad. To test the resistor. You are going to have to use a jumper wire to jump past the resistor. When you are jumping past the resistor. The motor is going to run at hi speed no matter which speed you have it set for. They will be no rwsistance to slow the voltage down to make the motor operate at slower speeds