I have a Whirlpool electric dryer, Model # LE7000XKN(orW)O. It runs like it is drying, but blows out cold air. I checked all vents and all are open. The timer has 3 different settings, 2 of them it will run forever, but the timed drying setting will work. If you can tell me which part to change, I would appreciate it. There is about 4-5 different reasons that it would not heat up. And I cant afford to keep buying parts till I get the right one. Thank You