had my tensioner and damper changed recently. parts
and labor for $400.00. it is a pain doing it yourself since
there are so many things you have to take apart.
my belt lost its tension and was told the tensioner was shot.
damper was changed for good measure. save yourself the
grief and ask a pro to do it.
PE - am surprised your a/c works despite the loose belt. yeh,
it will work but will cut out, in my case. took me a lot of headache
and research to trace the problem. a/c is suppose to cut out if
there are any distortion in belt cycle, and speed, i.e. loose belt, shot damper. this is the MB safety feature of the single belt technology running most MB cars. Most seasoned mechanics disagree with this feature since there are so many things and procedures to follow to identify the culprit. Hence, most of them suggest to by-pass the system (Klima control).