At over 43k miles, my 2012 Volt EV mileage dropped by about 5 miles overnight (now 37, was 46 summer and 41 winter). The cause seems to be that if the fan is on at any level, the accessory usage jumps to about 30% from zero (used to be around 6% with the fan on), even in Eco mode with nothing on. The only way to get my usual 41-46 EV miles is with the fan off. It seems like turning the fan on also activates the heater (accessory usage drops slowly as the desired temperature is reduced). Has anyone encountered this problem?