Ok so i have a 2003 trailblazer LTZ 4x4 with 124,000km's it is -16c here and last night my heater fan was working. then i lent my truck to off road bella and this morning the fan wont come on. The truck was left outside and not plugged in. the fan wont come on when the truck is running and it wont come on when i turn the key to run with out starting it so i looked at all the fuses and there all good and i have read about both speed sensors and bad connections what do i do so she has the truck at work right now so i cant do much. but when she gets here what should i do??