I posted a thread here last week about my block heater not working and one of you suggested I check the cord before I replaced the heater. As it turns out it was in fact the cord, which I then fixed with a new end from the hardware store. My new question is this: Does the polarity of the cord matter? Obviously the middle wire on the flat cord is ground, but if I got the other two mixed up will the heater still function correctly? Don't get me wrong, it works, but is it critical to get it right?