12V, 1.05A is 12.6W. 12.6W at 5V is 2.52A. Though I doubt it will draw that much in practise.
In a "normal"* 3 pin PC fan the blue/third wire is a tachometer signal so the system can monitor rotation speed. As such it should not be connected when using with a Pi.
Depending on the current the fan actually draws when running at 5V you may start to see undervoltage warnings from the Pi when running it under load or with power hungry USB devices connected. Prolonged under voltage can lead to system instability and file system corruption.
TL;DR: Don't connect the blue wire. Your system may become unstable under load.
*: For most values of "normal"
In a "normal"* 3 pin PC fan the blue/third wire is a tachometer signal so the system can monitor rotation speed. As such it should not be connected when using with a Pi.
Depending on the current the fan actually draws when running at 5V you may start to see undervoltage warnings from the Pi when running it under load or with power hungry USB devices connected. Prolonged under voltage can lead to system instability and file system corruption.
TL;DR: Don't connect the blue wire. Your system may become unstable under load.
*: For most values of "normal"
Statistics: Posted by thagrol — Sat Jun 29, 2024 12:28 am