Twice I've selected gear *up* and nothing happened.

Rob

 

 Twice I've selected gear up and nothing happened. I recycled the gear and out went the green.  Only in the cold, why?  I've been thinking would it be wise to open the dump valve before start up to release potentially built up pressure? I recall you had a door hang open when we were flying. Did you shut the breakers before opening the dump valve and recycling? Happy New Year