As with anything being sold, full disclosure of issues is the right path. With that said, it is almost always better to sell an item in ready to use condition. It is not always better from a cost to value perspective TO fix any deficiencies with the sale item.
Best to take account of the cost repair and whether you are able to do so for parts only, or if professional help would be needed for completion. Balance than vs. the lost sale value. Even if you come out a little worse for the wear, in some cases an item might sit and end up selling WAY below value because of the broken part(s).