My front heat will work intermittently. Sometimes I will park the Acadia, and it is working when I shut it off, then I come back to it and it doesn't work when I turn it back on. If I am driving and it's not working, sometimes it will just start to work. This is causing some serious problems because it is winter and I live in Illinois where you need defrost for your windshield, and if the heat is not working neither does the defrost. I was almost in an accident the other day... I was driving home and it just stopped working, my windshield started to fog up while I was on the interstate. I have taken it to the shop and they said there is nothing more they can do to diagnosis the problem until it completely stops working.