My sister recently had Wal-Mart auto services install a battery in her car. After a few days the car stalled and had to be towed to garage. The mechanic found that the wrong battery had been installed. It was too high, it overheated and welded the hood latch shut as well as caused damage to the underside of the hood.
The cost of the damage was $490. She had the Walmart receipt for the battery and installation, a receipt from the mechanic who fixed the damage clearly stating that the cause was the installation of the wrong battery, and pictures of the damages. She submitted these undisputable facts to Wal-Mart's claim management company (CMI) and her claim was denied.
They blamed the manufacturer of the battery not the morons that installed the wrong one. It appears from many other online horror stories that Walmart never takes responsibility for any damage caused by incompetent mechanics.