The air con in my A4 (2001-2004 model) isn't working. It has a dual climate control panel in the dash. there is an 'econ' button which has a small red light on it. When I press this to turn off the econ and turn on the a/c, the red light only goes out for the instant that I press in the button and comes back on again. Same thing happens even if I hold the button in. Anybody know what the problem might be??