How do you replace tensioner pulley on Mercedes Benz 190E?

To replace the tensioner pulley on a Mercedes Benz 190E, first, disconnect the negative battery terminal for safety. Then, relieve the tension on the serpentine belt using a wrench on the tensioner arm and remove the belt. Next, unbolt the old tensioner pulley from its mounting bracket and replace it with the new pulley. Finally, reinstall the serpentine belt, ensuring proper routing, and reconnect the battery.