I take it you are in UK. If so check out 'sale of goods act' this may come in line with 'reasonable expected service' even if the warranty has expired.
Give Aldi the chance by contacting them as they were the retailer, and under retailing laws in UK sale of goods act its their responsibility to change or repair the unit at their cost.
Use the answer sheet to your question to say how you got on.
Bob
March 2014