Last week, it cooled down a bit, here in Phoenix (yah, sure), and I thought I'd try my block heater to see how well it worked. Plugged it into the HD extention cord and it, immediately, blew the circuit breaker and my block heater. Big cloud of white smoke came out of the right side of the trucks engine compartment. It's a 20 amp. circuit breaker and the polarity checks out OK. 31,000 miles on the '03, 3500. I've never read of anyone blowing one of these up. Any of You guy's heard of this happening? Thanks. Joe F. (Buffalo)