I am sorry I made a general statement
I'm sorry I made a general statement regarding the resistor. This information might be true for the late model W126 only. My car have 2 circuits, the low power uses 1.5 mm wire with a 16 A fuse through a 30 amp. relay, activated by grounding through the refrigerant pressure switch (close at 225 psi, opens at 150 psi). The high speed circuit uses 2.5 mm wire. the circuit starts on the X 4/10 connector and it goes through the 40A relay to the fans. It is activated by grounding the relay with the high temperature coolant switch. I believe it closes around 105 degrees C. I did test the amperage with a DC Clamp-on Fluke meter and read 22.8-23A in the circuit without the resistor. Again I am sorry of making a general statement, this might be limited to the W126 late diesel model.