my heat/ac is not working - is it the blower motor?

Not what you want to hear, but at least it is a 3-series so most everything should be easy. You'll need to test the amount of voltage at the fan when you turn it on, if you are getting proper voltage at each position and the fan still turns off, you will need to test the fan resistor, and the fan independently. If you do not have proper voltage at the fan, you must test the switch(the fan speed on the dash) and wiring.