It's very common for air conditioning to not work when you switch it on for the first time after a long period of non use through the winter months. The gas will never condense to a liquid which then allows the seals to dry out, resulting in lost gas and a non functioning system. The answer is simple. Use the system frequently through the winter, or keep it left switched on all year round. For you though a trip to the garage for a re-gas is the first step.
