Well, when you buy a car your payment gives you ownership of the entire car.

There may not be a written contract or specification explicitly saying that the valves in the tyres are included in the deal, but they're your property nonetheless (in the absence of obvious errors like the dealer letting you drive the wrong car off the lot)

The customer paid for a car with heated seats present but inoperable. If the customer wants to modify their property, that's their business.