I had an interesting development while installing two RoadPro 12v outlets. Neither worked! After a night to cool off and think it over, I connected one to a battery and it worked fine. I got a volt meter and tested the house wiring for the lights. The hot and ground were reversed over the dining table and the BR reading lamp had the light fixture wired backward, which I had followed during installation, but the house wiring was correct. So I reversed the wiring of the outlets and they work fine. Is this sort of thing common?