Q: I've Mercedes ml350 and I was driving g under heavy rain the next day my signal lights, wiper blades, power seat stop working

Hello, thank you for writing in. The passenger (right) side of the vehicle (on yours and a lot of other vehicles) holds a computer system behind the fender (just under the floorboard). This is the box that controls the power distribution and function of several of the listed components you mention having issues. It is likely that this computer system got wet, which it is vulnerable to in the first place. The issues typically go away after the water dries, but extreme moisture will cause permanent damage. You will want to have the computer inspected to make sure it is okay, and look into water proofing it one way or another. For more help, contact our service department to schedule an appointment.