When the customer balks at repairing the switch just explain how many days or weeks they will be out when it fails or their liability exposure should it blow when someone tries to operate it and the lawyer finds out they knew there is a problem. Of course that is assuming the building survives the fire. The hardest part of any of these kinds of discoveries is the amount of time to failure and expressing that to the customer who will naturally want to wait as long as possible (read forever). No one actually know how long the customer can go before there is a deadline.
