Don't wait until a rainy day to change worn-out windshield wipers. My translation: No espera hasta un día lluvioso a cambia las limpiaparabrisas gastadas. Translation in my learning material: No espera hasta un dia lluvioso para cambiar unas escobillas ya gastadas. Can you help me understand when to use "a cambia" and " para cambiar". Is it that the "a" must indicate going from one place to another and so it's correct to use para since it means "in order to" rather than " going to ". Am I on the right track? Also, if I may ask another question. I'm not sure about the "ya". Since it means "already", isn't it redundant in this sentence? Gracias para sus ayudas !