M103 (W124) fan belt tension setting

[taaboo]

Friends:

I'm getting ready to install new serpentine belt on the 300TE. The MB shop manual speaks about some graduations on the tensioner, and to tighten it to pretty much the last notch. My tensioner does not have the graduations, only a 'triangle' marking with no graduations. I had the existing belt off a couple of weeks ago and tightened the tensioner fully (pointer all the way to the edge of the 'triangle' when reinstalling ... the belt seemed soooo tight - I could barely deflect it, I'm comparing it to the normal 1/2" up or down I've always used on my other cars - that I loosened up the tensioner to about half way.

What's the best/right way to adjust tensioner which does not have the graduations????

Many many thanks -

Brian
89 300TE 157,xxx
84 733i 5speed 138,xxx