Are you POSITIVE that you did all the conversion wiring correctly? You HAVE to follow the directions in order if you have never done it before. But, no, the solenoid valve should NOT be hot all the time. Part of the 12 to 5 conversion has to do with the Reversing valve wiring. The NEW 12 button boards, the default is for the unit to cool instead of heat on the Heat Pumps. So, the default on a 12 button is to have NO power to the reversing solenoid and it will cool. If you power the valve it will heat. That is why I think you miswired the conversion kit. Doug