Hello rob,
SoGA is the 'Sale of Goods Act' It enshrines your statutory rights that are automatically established when you make a new retail purchase. If goods are faulty you are entitled to a full refund or an FOC replacement.
When you buy anything new a contract is made between the buyer and the seller. The seller under SoGA is required at the time of sale to supply goods that are free from design, material or workmanship defects. The goods must be fit for purpose and of merchantable quality. This is the basis of your WARRANTY - even if no paper work is produced.
If goods are defective at the point of sale then the seller is legally obliged to remedy the situation. what that remedy is depends on the goods their age, and the type of defect. The difficulty sometimes arises when a fault becomes apparent some time after the date of sale, and then establishing it was actually present but not detectable at the time of sale.
In extreme cases the matter may be taken to court, where a judgement based on the balance of probabilities will be made.
It is important to note that the seller is legally responsible, so that is why when you use a credit card or finance deal, the credit provider is the seller, as you are effectively buying from the credit provider. (The same does not apply to Debit cards or overdraft)
There is no such thing as a fixed term warranty, A warranty remains appicable for the life expectancy of the product, though in practice claims of more than 6 years have never been successful. Obviously the life expectancy of a products varies, and perishable goods may be hours where as granite slab would be years. Don't forget though, the fault must have been present at the time of sale to invoke a warranty claim.
Warranty liability rest only with the sellers - no one else.
The above is a short outline of your statutory rights of warranty under SoGA. They should not be confused with the manufacturers Guarantee, which is an entirely different beast.
Manufactures are not obliged to have any direct responsibilities to the end-user (unless they sell the product direct in which case SoGA kicks in) If a manufacture offers a guarantee, it is a gift, and it can be made with many different clauses. Even though money does not change hands, it is still a contract, and both parties are beholden to the terms of the contract. So for example they are usually time limited, they may require certain actions to be carried out such as servicing, and it may stipulate who does the service. It may exclude certain items, or set different terms for particular aspects of the product. Guarantees are not automatically transferable.
With items like cars and caravans the manufactures Guarantee often mimics the sellers legal Warranty response. This is useful because it allows the end-user to have what should be warranty repairs carried out by other dealers, and paid for by the manufacture under their guarantee. whilst this often happens, it never affects your legal rights to warranty with your seller.
Now I made a number of assumptions based on your original post. I thought that the caravan was much younger. i.e only a few weeks old because you mentioned testing, and that something had burned out on the circuity board. with the more recent information I see I was wrong on those two critical points.
However as you now tell me it may be a revision issue rather than a physical damage issue, and the age the complexion of the situation changes a little.
If the product was physically damaged, then you would still have a case to insist on a replenishment part. The issue is that following a product fault, the remedy should reinstate the product to the condition as if no fault had occurred. If a circuit board was damaged with burn marks, and components were replaced then the fault would remain obvious and will devalue the product.
In the case of reprogramming, no obvious damage would be present, and thus a warranty repair (subject to the repair working properly) is a viable remedy and should be considered.
If the caravan was less than 6 month old, you would have had a stronger case to call for a replacement part rather than a repair as the balance of probabilities is swayed in favour of the end-user.
SoGA is a powerful tool in the consumers armoury, and whilst it is their to ensure that consumers get a fair deal, the important word is fair, It is designed to be fair to both the seller and the buyer. If a claim is disputed and it goes to court, the outcome will take into account the accuracy of the claim, any obstructive actions by either party, the true value of the product, and any unreasonable usage, etc. so it pays to be scrupulously honest and fair when asking for warranty work to be done.