We had this problem with our ambulances when water would get in during car wash and storage. It was a big problem since our outside compartments with emergency equipment were getting impossible to get into (huge no no during the call). We solved the problem by putting medical tape over locks when in storage or when going thru the wash. But if by any chance it happened my windmill torch/ key heating technique worked fine. Also WD40 was used very richly in order to keep them in tip top shape.

Matt