I've had the same problem and tried the same as you. In this cold weather I've taken the reciever off the wall and placed it next to the transmitter - no red light at all! Not a permanent solution obviously but it seems it's nothing to do with batteries and all to do with the unit being rubbish with no range and/or no power in the signal. Nothing on their website either, although I don't think I'd admit to it being mine if I had a choice!
Mike
February 2009