On the fan controller (see pic) I have various fans attached, from left to right: Channel 1 has one Noctua NF-A12x15 PWM (rear), Channel 2 has three Scythe Gentle Typhoons (side rad), Channel 3 has six Scythe Gentle Typhoons (top rads), and Channel 4 has two Scythe Gentle Typhoons (front).
The problem is that Channel 2 doesn't give me a rpm signal even though those are the same fans as the top has (Channel 3). I checked the cables and they are all the same, same goes for the Y-cables (3-pin to three or six 3-pin). I also checked if it was a channel issue, it wasn't. Me thinks it has to do with one of the fans..