!993 MB 190E 2.6 Belt will not tighten

[gbradcsi]

What are the indication of of a bad belt tensioner?

i like to know if the tensioner itself can prevent the serpentine belt from being properly tightened. this has been loose for awhile now i found out, a new belt and shock did nothing. changed the adjusting rod, no change. the rod even stripped out when tightening it, so it has a new adj. rod now. the tensioner will move as you tighten it with the adjusting rod and it places tension on the belt, but the belt is still loose. yes, have a new corect belt. the problem did not start with a belt change. the old belt is still good.
one of my family members is working on it. i remember when i owned the car i was able to tighten it so it feels tight. NOW it deflects with VERY light finger pressure more then 1/2". it is loose. i don't see anything missing. it's threaded right. the car runs, but you can't use the A/C because the belt is too loose ans splashing water on it results in the belt coming off. so it's loose. i have adjusted many belts over the years ao i know that this is not right.
i don't know when this problem started. any ideas on this? it may have been after a waterpump change, but the same pulley was used. everything is original on the car. i wonder if a bad tensioner can prevent it from being adjusted properly? i am ordering a new tensioner.
thank you in advance.