buyer/seller integrity question

I just sold a car to an out of state buyer & after recieving the car he is not happy with it, thinking that I screwed him: radio/gauges don't work, has rust, brakes pull to right, fuel stale. I bought the car & only drove it once or twice then it has set for at least a year & it drove OK & no pull that I remember & I didn't notice the gauges not working. all I posted is that it runs/drives well which it did for me & I took alot of pics of it tho not of the underside which I am assuming is where the rust it. I lost interest in the car when I bought it & never did anything with it. he wants a partial refund. Am I at fault here? Thank you for your time. RR