I have A 2011 Buick La Crosse. gets wet want start on 2011 Buick LaCrosse

Everytime my car gets wet either from the rain or from washing it, it want start. the battery acts as if its dead but all the electrical system goes crazy. wipers come on and cant shut off. the lights go on and off. I can boost it off and after I drive it, then it starts ok. The Dealer cant figure out what to do. There computer doesn't show any codes so they don't know what to do. Is there anyone that can help on this

Asked by for the 2011 Buick LaCrosse
Agree with1
Thanks a lot for the reply. I have taken it to another dealer to try to find the problem. I did have it at the one in Vicksburg and they never could find the problem. They told me that it was the battery and then I found out from another mechanic there, to go to another dealership and have them check the car out. So That's where I am now. these new cars are so hard to work on and I am lost on them
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I would do a real thorough leak test with a water hose and then inspect the interior for leaks espcially near ny control modules orfuse panels. I have seen this on other car models.
Thanks a lot for the reply. I tried to run the water on it to find any leaks. checked the sunroof and ran some water over the hood and still no luck. But the next morning it would start. And last Saturday I changed out the battery. Still having the problem