Well, I procrastinated all winter and just replaced the Monovalve. Problem solved! 40°F out of the center vents at highway speed.

Actually, since we do have winter here in Arizona, I wasn't that concerned as I was getting plenty of heat. So, when the belt tensioner horked, I replaced a bunch of stuff while I was under the hood.

There are threads after threads on this forum regarding the belt tensioner on the M103, but let me say one thing about it here in this thread. It is not a job for the weak and hasty people. And DO NOT tighten the large (19mm socket) pinch bolt until you've adjusted the belt with the adjusting nut.

Anyway, much appreciation to all who help me solve my creature comfort problem.

Regards,
Michael.

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1992 300CE - 157kMi (my white beauty)
1992 300CE - 220kMi (sold)
1990 300E - 189kMi (sold)
1990 300SL - 102kMi (salvaged parts available)
1986 300E - 230kMi (salvaged parts available)

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