With DEF on, there is a tiny resistance of 0.3 ohm between pin #8 and #3 of the CCU. Yet the blower doesn't turn on.

I've tried hot wiring the CCU plug wires (#8 to #3), but the fan didn't turn on. Should it? If so, maybe the speed controller is (suddenly) faulty?

I've tried using the low speed (Speed 1), but don't hear a peep (I know it's quiet, but still). I'm pretty sure the CCU has the low speed setting working.

I'm wondering if maybe there is a different connection to tell it to turn the fan on (regardless of speed)? I've hotwired the blower speed controller plug so POWER goes directly to SPEED 6 OUTPUT. And it turns on. But I'm suspicious my CCU was re-soldered wrong.

Any clue what the "Automatic Blower Speed Input" does (#1 on the speed controller, from C2/#5 on the CCU)?