I am having trouble with 2006 f150 . When it gets really cold outside minus 10 or so the heater fan doesn't come on. If I put truck in heated garage and it warms up it works again.I seems like a bad connecting somewhere I think . Any idea's anyone.?

 

Blower motor resistor. $20 and a 5 min fix behind the glove box. Had the same issue and this fixed it.