is anybody else finding that their heater's recirc button turns off after only being on for a few minutes??? when trying to warm the inside of my truck up in the mornings and at night i press the recirculate button to the right of the A/C button so that the warm air recirculates and gets hot. after no more than a few minutes of driving i will look back at the button and find that the little amber light if OFF!!! i am SURE that i am turning it ON and NOT on defrost and this light keeps going off. ANY IDEAS???????