2002 chevy silverado 2500hd duramax. the fresh/recirc door doesn't work. the lights on the dash change when the buttons are pushed, but it stays in recirc mode. Are there free repair manuals on here somewhere? not the owners manual, but a full do it yourself service manual. hoping for a free download. if not whats the best Service Repair Manual For 2004 Chevrolet Silverado 2500hd Duramax .