Ebay does not ALWAYS side with the buyer in situations like this..I recently had a woman purchase a perfectly good laptop from me. It was a gaming rig, but a couple of years old. She had it for a few days, left good feedback, then started to complain about it. Said I sold her a broken pc, said it wouldnt run the game she wanted. I pointed out the pc didn't even meet the min req for the game she wanted to run. A few days later she tells me the video card is toast, and one of the hard drives don't work and that she wants a refund. I told her I could cover 1/3 of the cost to repair if it would make her happy but that this was a fully functioning machine when it was sent to her, that I had played Skyrim just the day before sending it in the mail to test it out, and that I would not accept a broken machine back.
Enter ebay. I am the one who actually escalated it to ebay, I was tired of her harassing emails. It took several days but ebay did side with me. They are not just autobots that issue refunds to anyone who cries foul for any reason. Depending on the wording of the auction you may or may not have a case. If the seller stated in the auction this was guaranteed 100% functional with no issues what-so-ever I would open a case. If no such claim was made, you could open a case but you likely wont win it. Better to talk with the seller and see if he would help out with the cost to repair. If you have not yet left feedback you may find he is willing to work with you a little..maybe?