Mmmm......I doubt the Lexus dealer will be willing to change the relay as this means removing the switch assembly, opening it, sourcing a relay of the same type, and soldering it in. Lexus dealers simply don't this kind of electrical surgery. However, as you have a warranty you can insist they change the complete wiper switch. I wish I had insisted when it was under warranty. Each time they said "nothing we can do if we can't see the fault". I think this is a cop-out as this relay fault is fairly common. It is due to owners trying to make the wipers operate on frozen windscreens thereby inducing excess current through the switch relay.