It is great that you found the resister. I could not find it in my 300SDL and I do not want to lift the fuse box, too much hassle.

Anyway, I am not sure what do you mean by slow speed function. The aux fan can be control by K9 and K10 only. Klima plays no part in it as far as I can determine. K10 is only a ON/OFF relay controlled by the rec/dryer high pressure switch. The 12v from fuse 13 goes to terminal 30 of relay, through the relay, to the resister and then to the aux fan. May be it can attenuate the speed a little with the resister. I am not sure.

K9 is control by the temperature sensor on the engine block, switch at 110 degree. The relay is connected directly to the aux fan, by-passing the resister.

I think the Klima relay is all to do with the compressor control and monitors the engine speed. I may be wrong as I have not worked on this part of the circuit before.

Hope this help.

__________________
Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

1 X 2006 CDI
1 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.