I have a heat pump for my house's heating and cooling. We had our first hot day of the year last week, so I switched it to cool mode (heretofore it had always been in heat mode). When in cool mode, however, i have no air flow at my vents. The air handler is on (there's sound), but it's not as loud as it usually is. I think the fan isn't running. I opened the chamber where the air filter goes, and I didn't feel any airflow. Furthermore I see ice crystals forming on the refrigerant lines. In heat mode, everything works fine (the fan comes on, and there's plenty of airflow).
Is this a problem that I can diagnose/fix myself, or should I call an HVAC company to look at it? It's an old system I'm planning on replacing in the next year or so, so I'm hoping to not put a lot of money into fixing it if possible.