Ahh, winter. When the number one problem people have with their carsis.. lack of heat. A full season without using the heater and a sudden need for it can mean unexpectedly going cold. For the most part, in-cabin heater problems for your car boil down to two issues: nothing to heat the air and no way to blow the hot air if it is there. Either problem is relatively easy to diagnose if you know what to look for.