Thanks GBenz, MB Doc, & Blackmercedes!

I had checked the belts, but tightness doesn't mean it wasn't slipping.

Is it easy to change the evaporator sensor? A DIY job?

Thanks,
Neil.
99 E300D
94 S350D
83 500SEC euro
79 406 Unimog

gone but not forgotten:
84 300D
84 300SD