If its still in warranty, take it back to ALDI, if its out of warranty, just buy a new one. If you have had three years use out of it, it owes you nothing, you have had your money's worth.
It would cost you more to repair it than it would to buy a new one. I have had good tools and bad tools from ALDI, their mains power tools were well worth their money, the rechargeable ones, have not been so good, but with a three year warranty, you can not go wrong.
They are so cheap i usually buy two at a time, then i have one spare just in case i have to send one back.
Its_me_Init, October 2010