The drivers side headlight will come on at various times

Problem is intermittent, but the drivers side headlight will come on at various times, usually overnight and will drain the battery. Ford doesn't understand the issue, I have researched on line but the problem seems to be consistent with both headlamps, mine is only drivers side. Thought? I have hanged out lamp and ballast, cleaned the socket with electrical cleaner. Could the relay cause this issue with one side only?