You dont need to replace the tensioner, unless its old and noisy. Access is poor, you need a 15mm swan neck spanner to remove the tensioner and/or idler, and also to slacken the tensioner to remove the belt.I take it from the pic which Ian kindly posted, that item 7 is the idler which I will remove when removing the compressor. Is item 5 the tensioner and should I replace that at the same time? How easy is it to replace the belt/tensioner? Access looks a bit limited.