Question Rear fan at max speed after installing AIO

[nikkitheknife]

I upgraded my build to an AIO liquid cooling kit. Now my rear fan is running at max speed. The AIO seems to be working fine, other fans are working fine, it's just the rear fan. Went into BIOS and tried to change it there, but it isn't responding and just continues running at full speed. It was not doing this before installing the AIO. Not sure what to do next.

 

[Lutfij]

Welcome to the forums, newcomer!

We're going to need a little more info. When posting a thread of troubleshooting nature, it's customary to include your full system's specs. Please list the specs to your build like so:
CPU:
CPU cooler:
Motherboard:
Ram:
SSD/HDD:
GPU:
PSU:
Chassis:
OS:
include the age of the PSU apart from it's make and model. BIOS version for your motherboard at this moment of time.

I upgraded my build to an AIO liquid cooling kit.
What were you working with prior and what did you upgrade to? A link would help us two fold. Which header on your motherboard is the rear fan hooked up to?

 

[alceryes]

What do you have the AIO fan plugged into? Motherboard fan header or standard 4-pin molex? If it's the motherboard header which one?

 

[Paperdoc]

Rear fan details would help. ONE reason for this can be if the fan is an older THREE-pin fan. That is, its cable has THREE wires and ends in a connector with THREE holes. That CAN be plugged into a mobo fan header with 3 OR 4 pins. IF you plug an older 3-pin fan into a 4-pin header, MOST headers offer an option in BIOS Setup for the MODE of the header. Mode is the type of signals sent to the fan to control speed. A 3-pin fan MUST be fed by a header using the older Voltage Control Mode (aka DC Mode). A 4-pin fan should have the header set to PWM Mode.

Also make sure the header PROFILE is not set to Turbo or Manual or something like that. It should be set to Standard or Normal.