Before attempting this job. DISCONNECT the BATTERY.
You need to Tension the tensioner spring before removing it.. If you look at the annotated picture below I have indicated the two lugs on the side of the tensioner that are used for that purpose.
Remove the Offside wheel and innner plastic arch liner to help removal and refitting of the accessory belt.
There is a special Renault tool that is used to pull the accessory belt tight, in turn this pulls the tensioner closed and compresses the spring. You could use a bar inserted between the belt and the sump, then use this to force the belt downwards to compress the spring.
Then there is a small plate with two square holes in it at each end that is used to clip over the two lugs to keep the tensioner secure.
You then release the pulling pressure on the belt and remove the tensioner from the vehicle. This will allow you to remove the accessory belt easily.
Remove and replace the alternator. It is secured by 1 16mm Long Nut and bolt at the top.. And a single 13mm bolt at the bottom. Refitting is reverse of removal.
When refitting, you MUST
use a NEW
accessory belt, Do Not reuse the old one..
Route the new belt over the pulleys, It helps having two people. Then refit the tensioner to the vehicle. The tensioner can slide up and down on the mounting bolts.
To tension correctly you must push the tensioner onto the belt until the slack is taken up. Tighten the securing bolts.
Then again pull on the accessory belt to pull the tensioner spring up, this will release the locking plate allowing it to be removed easily. Then release the accessory belt.
The difficult part I can see is actually getting hold of the tensioner locking plate.. You could buy it from Renault I guess, but at what cost.. I don't know..
The locking tool looks like this