If I don't drive my car for a week, the car will not start. I seem to have narrowed it down to fuse no6 ( radio and interior lights) in the footwell. I have the switches turned off, removed all the blubs, booth and doors, not the sun visors or glove box, this stop the drain, in September I had the car locked for seven days, with fuse no6 removed and car started ok. I have noticed that when the engine is running, tested a few times going to work on a 30 mile journey, with multimeter connected into the lighter socket, I get no more than 13.4 Volts on the DC system. I changed the battery as well at the start of the summer. Any ideas?