You need to identify the K9 and K10 relays, low and high speeds. The low speed relay powers the fan through a resistor which I think is close to the drier on your model. Looks like a ballast resistor for an old ignition set-up.

Be sure power gets to it and through it.

K10 should be position "B" and K9 should be "C" K10 is low speed which is the one that comes on for AC pressures high.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician