If you take a car back to a buy here pay here do you still have to pay the balance?

Yes, of course. Read your contract. A BHPH lot offers alternative financing to people who can't get financing otherwise. The terms are the same as any standard financing agreement. Bringing a car back, whether voluntarily or involuntraily is still a REPO. So, the dealer has the option to sell your repo at whatever price he accepts and sue you for the balance. This isn't Wal-Mart!