The legislation that governs all of these types of transactions -whether a new or second-hand product is purchased – is contained in Real Decreto Legislativo 1/2007 – Ley General para la Defensa de los Consumidores y Usuarios (Consumer Protection Act).
Goods bought from a commercial enterprise must conform to their description or any demonstration of the product carried-out by the seller, be apt for the use typically associated with a product of it’s type and be capable of performing any particular function that the buyer has drawn attention to and which the seller has confirmed that the product is capable of performing.
If any of the above circumstances apply, the buyer may demand a repair of the item, substitution, a lowering of the price or the return of their money. Normally the return of the purchase monies would be appropriate when none of the other remedies can be offered or are not done so in a reasonable period of time. A return of money may not be appropriate for truly minor deviations from the description or performance of the product.