The motherboard has three chassis fan connectors (CHA_FAN1,2,3), one 4-pin CPU fan connector (CPU_FAN1), and one 3-pin CPU fan connector (CPU_FAN2).
I connected my CPU fan to CPU_FAN1 since the connector is a 4-pin.
I have 3 chassis fans. Although all three chassis fan connectors work, I am not able to control the speed of the rear fan (CHA_FAN1) for some reason. Because of that I connected the rear fan to CPU_FAN2 instead which seemed to work. Not only that, I am able to control the fan speed on CPU_FAN2.
My question is, although everything seems to be working correctly, will it be safe for the motherboard/cpu/fans in the long run if I connect a rear chassis fan to CPU_FAN2?