Not sure. As far as I know its either the relay or the pump itself. If water is in there, the cold winter temperatures can cause the water to freeze and damage the pump or at least prevent it from spinning. I would wait at least until it warms up above freezing and check it then. And pull the hoses off the pump to drain any water.Does anyone know, if the air solenoid valve is not working, can this cause the air pump to not work or engage on start up?