Heating in 2007 Jeep Commander
The heating (air) in my car will not come on. Even if I let the car run for 15 minutes before driving it the heating will not come on. I have heard a "knocking" sound from time to time, but the heating still won't come on. Randomly it seems it will come on (NOT full force) for like 1 to 2 minutes and then it goes out again. What can be the issue and is this expensive to fix?