My '99 GMC Sierra has been acting up lately. The battery is original, had it load tested and it checks out ok. If the truck sits for more than a day than the battery is low or flat when I go to start. I verified the only accessory that is on is my cell phone plugged into cigarette outlet. Has anyone else experienced this? I am wondering whether it has something to do with the cell phone or whether it is some other issue....
Thanks, -Mike