Baffled on return policies

[timberwolve-79]

I sold a vintage item (part) in collectibles for $4.00.

I stated I didn't know if it worked or not and was sold as is.  I didn't actually list it as "non working for parts only".

Buyer wanted to return as "item not as described"

I tried telling Ebay that it was described correctly. 

Not only did Ebay take the money back, the buyer gave me negative feedback. 

What did I do wrong?

[2013fitzp]

You went wrong by not listing it as parts not working. Always, always, list anything that might have any type of defect like that. I sell built working laptops as parts not working because of what happened to you. 

[bonjourami]

you didnt list in non working, parts only, category..and to say you dont know if it works or not, and 'as is'', is never a good idea, and leaves you wide open for a snad..sellers are supposed to know what they are selling.