1st take a couple of digital photos of the wiring on ALL of all 6 batteries. If your Bus set up like our '06 Phaeton, I had to pull the 2 6Volt batteries toward the front of the RV completely out of the compartment. Next take out the 12V battery toward the front of the RV, then slide toward the front of the RV the rear most 12Volt battery and remove. Install in reverse. Our OEM 12Volt starting batteries only lasted about 4 years of fulltiming, OEM house batteries lasted a little over 5 years. We're working on 10 years in the Phaeton now, so the cycle is overdue to start again.