The knob in the dashboard that controls the heater / aircon fan only works at max speed. I gather there's a resistor or resistors that control the lower speeds of the fan. Where is it? I've ripped out the centre section of the dashboard, radio, ashtray, etc. I've reached the back of the control knob; the wire goes away into the darkness towards the left. I've aleady taken out about 20 screws to get this far, and about 6 plastic panels. Is it behind the glove box? This is a right hand drive Hymer. Help!!!!