You can turn it in to your insurance company, but it would be up to the insurance company guidelines and state laws to authorize/offer coverage for this electrical issue. Your insurance agent or claims adjuster of your insurance provider should be able to tell you if this water that leaked into the trunk of the Mercedes during the car wash would be covered by your comprehensive coverages.

If this incident and damage is not covered under your comp coverage then you should read through your wife car's warranty to see if this would be under the provisions of the warranty. If it is a defect in the car's trunk that allowed it to leak water during the car wash and short circuit the fuse box that is located there then a manufacturer's warranty may cover it.