So my heater quit working on the low and medium level about a year ago but continued to work on high, and of course I didn't pay it any mind. Now the heat goes on and off randomly but most of the time it goes off after about 5 minutes and doesn't come back on until I turn the car off for a while and turn it back on. My car doesn't over heat or anything. What is going on? Please help! Oh and I believe it is a 3.5 engine.