You can schedule air conditioner cleaning at any time of the year, but the autumn and winter months are a good time because you can remove a lot of accumulated dust, mould and bacteria from the summer period. It’s a bad idea to start running the heater if your air conditioner is dirty as it can spread mould, pathogens and other nasty airborne particles. You can also opt to clean your air conditioner during the spring and summer months if you haven’t had a chance to schedule a clean before then.