I've hooked up some test-switches today for the fan-mod, and thought I might as well use two switches for either side, if I didn't really need max cooling. However, it seems that either switch (either relay 20 or 22) activates both fans?

Are they already linked together somewhere else, and is it thus only necessary to ground-switch one of the two relays?

 

Seems to me you would have to do both relays for low speed/high speed fan operation since they are all separate relays.

 

Yeah but the weird thing is when I do one relay only, both fans come on. So I was wondering if the 85 control pins of both the 20 and 22 relays are already linked together before the relay tray. Needing two relays I understand, you'd want a separate high-current circuit for each fan. But maybe the control wires are already linked.

 

Very possible. Most of the time the relay circuits simply provide a path to ground to initiate/complete the circuit, so they may have a common ground. I suppose you could look at the back of the relay panel to see if the ground wires are connected.