As Chris has said, it depends.
Strictly by auction rules you are bidding to buy and once the item has been won its yours, you do have time to go and view the item before auction close. However, other factors like distance selling regulations come into effect where you have 14 days to return an item regardless if it meets a description or not.
If your item was described as working when last used but requires X,Y,Z then you needed to bring such items with you, if not then it's reasonable to see the item working before handing over the cash, if they have problems with that - tough
Darran