Now when it starts to work, I heard it works for about 3 to 4 minutes and it will stop of 3 to 4 seconds and starts to work again for 3 to 4 minutes again stop working for 3 to 4 seconds; it will work like this for about 40 minutes to get to the set temp. But before, it will starts and non-stop working to get to the temp, why this stops happen now? Please help!