PayPal allow you to raise a dispute up to 6 months. I have used this myself as I bought an amp that said it had 2 years warranty and it failed after about 4 months and after a month of being ignored I raised a dispute. PayPal emailed me a returns label and a couple of weeks later issued my refund.
Not after 6 months, it's up to.
But, PayPal will always side with a buyer, so even if it's not faulty, but you say it is, you'll still get the returns label and the refund. I've been on the sellers side of this and don't accept PayPal anymore due to this, only cash on collection (or bank transfer/gift if I sell on the members market here)