DODGE NITRO 2011..LIKE SOME OTHERS HEAT BLOWS COLD AIR BUT NOT ALL TIME

That's most likely a heater core beginning to plug up with sand. If you flush the core out before it completely plugs, you might be able to save a bunch of money. You certainly don't want that core replacement bill.

It,s the blend door motor. The teeth on the gears are made out of plastic and tend to wear slowly, this causes the motor to work some of the time and not to work at other times.When you first start your car, turn off your radio then turn on the heater . Listen for the blend motor trying to open the heater door, it will sound like a series of clicks. This the motor trying to open the door. There are two motors just above your right foot on the drivers.the large plastic dash panel under the steering column is hinged to open down.no need for tools , just open the trash container on the left and pull the panel from there.after opening, pull the panel all the way to your left and remove the panel to get it out of your way. Now look up toward the center tunnel and you will see the first motor,this one controls the main heat and is the first one to wear out since it moves every time you start your car. The one just above and further back is the one that control air direction. Each motor has two torx screws and an electric cable which are very easy to remove and replace. Good luck