I am trying to hange the serpentine belt on my 09 lancer rallyart and it keeps slipping off

Locate the two belts on the left side (passenger side) of your Mitsubishi Lancer. The outer belt is a serpentine belt, operating four pulleys and the inner belt is your alternator belt.

Follow the serpentine (outer) belt to the three pulleys lined up vertically near the front of the engine compartment. Locate the middle pulley, which is the tension pulley for the belt.

Loosen the bolt on the middle pulley with a socket wrench by turning counter-clockwise. Do not remove the bolt, just turn it a couple of times. Loosen the tensioner bolt on the side of the of the pulley, facing the front of the vehicle.

Remove the serpentine belt and then loosen the bolt on the alternator. With the alternator loose, move it forward so that the alternator belt loosens up and then remove belt from the pulleys.

Install the new alternator belt by placing it over both inside pulleys. Tighten the tension on the alternator belt by moving the alternator back and keeping tension on it by holding it back with a long screwdriver. While the alternator belt is tight, use a socket wrench to tighten up the bolt on the alternator.

Place the serpentine belt back on the pulleys and then use a socket wrench on the bolt on the front of the tension pulley. Once the serpentine belt is tight, tighten up the bolt in the middle of the tension pulley.

Start the Mitsubishi Lancer's engine to test the alternator belt and make sure it is working properly. Once you have verified it is working, turn the engine off.