I have a Whirlpool Generation 2000 oven. When im using the oven the light comes on normally when you pass about 180 degrees. However this then goes aoff after 5 minutes and the oven cools down. If i then increase the heat the light clicks on again but then the same problem occurs after another 5 minutes. Essentialy all i can do at the moment is use my oven at the max temp of 240, anything less clicks off and the oven is barely warm. Can anyone help please?