Does anyone know what could be wrong with an 2005 Monte Carlo. When the heater or ac is turned on and sometimes nothing comes out. When I turn the switch on I can hear a click noise but sometimes the heater or ac won't blow into the car.

 

sounds like possibly a bad blower motor. before you spend the $$ to replace it, check the wiring and the fuses, you said it clicks- that could be the sound of a short or a fuse popping, check your wires, take out and inspect/clean your fuse and replace the fuse if broken. or it could be a fan switch either bad or the wiring harness has shaken loose or something. keep us updated.