I've done the test in the dark and sure enough light went out after 2 minutes. I sat in the car for another 10 minutes and nothing happened. Maybe I do just need a bigger battery. Plenty of time between now and next April when the car will parked up for 2 weeks. Thank you for all the replies, I'll master this car one day!!Thanks for that Marty, I'll be out soon sitting in the car, in the dark, like a total pervert! I've just watched the vid for the filter that you've developed and I'll be ordering one if necessary. Thank you again for your help.