1999 Seville, generally after a rain or car wash, the gas door cycles as does the trunk open. If will run the battery down. Has anyone experienced this problem?

 

I too experienced this problem once. It was during an extremely bad thunderstorm near Houston area. I fixed the problem by "resetting" the electronic system with my keyless remote. I stood near the vehicle and held both the lock and unlock button for 7 seconds. This fixed my problem. Haven't had the problem since. Hope this may work for you.

 

I believe that I have found the problem. The left side drain for the sun roof was leaking. I plugged it up at the roof with some plumbers putty to test about two months ago. I have had no problem since and have been though carwashes and heavy rain.