Where to plug radiator fan(s)

[jrglol]

I'm looking forward to buy a 120mm liquid cooler (Deepcool Maelstrom 120T to be precise), but my motherboard only has 1x CPU_FAN & 1x chassis fan header. Do I plug the pump to the CPU_FAN and the radiator fan to the chassis fan? I've been searching around the internet for some time and most of them have more headers than mine. I have 3 PWM fans connected to the motherboard (using a splitter). My motherboard is an ASUS Prime B450M-K.

 

[bmockeg]

I would get a Molex 4 pin adapter and connect the 3 fans to your power supply.

 

[Tolis_GR]

Use the CPU_FAN header for the cooler fan and the Chassis_Fan header for the pump.
Now for the rest of your pwm fans, you ll have to uncover some information from your mobo and your fans. Most headers will supply an amperage around 1 A, and many fans draw around 0.25A which leaves some headroom to install more than one fans there (three is ok, four is way too much as it will operate near the amperage limit). Pumps also draw around 0.2A but try to find more info about your specific cooler pump and fan's amperage.
My suggestion, add one more fan to the cpu header, and one more fan to the chassis header along with the pump.
Leave the third pwm fan alone and plug it directly to the psu line with a converter

 

[Greeko85]

I'm personally against 120mm AIOs as their performance is subpar to a decent air cooler but if you have your heart set to it then simply plug the rad fan to the CPU_FAN header and you can connect the pump straight to the PSU with a molex adapter (you generally want the pump to work at full speed anyway)

*edit typo