Can you define "engaging"? Meaning something electrical or perhaps a driven accesory?
As far as driven accessories, the only thing I can think of is the AIR pump which is moounted on the right side (at least on the 5.6, not sure on the 4.2). If the pump is malfunctioning, possibly binding, it might load the engine to the point it tries to stall, but the belt would give out quickly I think.
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.