I may be the only one who does this, but......
When I change the belt on the M103's, I've found the easiest way is to remove the bottom alternator bolt, loosen the upper one and piviot the alternator until the belt slips off. Then when I reinstall the new belt simply pivot the alternator back to the point where the lower bolt slides in place. The tension is usually correct (or is close with only fine tuning with the tensioner) and takes all of 5 minutes. I'm wary of messing too much with the (in my experience) delicate tensioner assembly.
Am I strange or incorrect in doing this? Thanks, Klaus.....
'07 R320 CDI " Manta Ray"
'62 300d Adenauer-350 Chevy
'12 VW Passat TDI 6/speed
'03 Dodge Ram 3500 - "Clifford, the big red Dodge" - Cummins w/6-speed
'68 Mustang fastback