It may be that you have a low refrigerant charge. That would explain both the inefficient cooling of the A/C system and the failure of the aux fans to engage when the A/C is running. Pressure testing will give you the answer. You may also have a bad monovalve causing heat to come out of your vents.

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1988 California version 260E (W124)
Anthracite Grey/Palomino
Owned since new and still going strong and smooth
MBCA member

Past Mercedes-Benz:
1986 190E Baby Benz
1967 230 Inherited from mom when she downsized
1959 220S Introduced me to the joys of keepin' 'em goin'

There are only 10 kinds of people in the world--those who understand binary and those who don't