I had wondered if the mech had bothered to check the aux fans...
You should be able to test at least part of the aux fan operation by starting the car and then turning on the A/C. The fan should run with the AC on. It might take a few seconds, but the fan should turn itself on with the a/c running. That would at least give you a place to start the diagnosis, you will know if the fan will run at all. OH, if the charge in the a/c system is low, freon level, the a/c compressor will not kick on, and in turn the fan might not turn on...so, if the ac is in the on position and the ac air inside does not get cold, and the fan doe snot come on, it is likely because the ac freon level is low, not a aux fan problem

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Christopher Henkel
1990 190E 2.6 - Arctic white SOLD
1986 190E-16v - Blauswartze
1993 300CE - SOLD
2003 W208 CLK 320 Cabriolet - Magma Red