post error message during boot " fan detection error"

[pull-lift]

Hi hello to everyone i'm new here and hope to find some help from the community?I changed my cpu in a hp z240 sff and at every boot i have an error message saying: Post error  "error fan detection" i make "enter key" and the computer runs well, i have plugged the fan from the cpu and it's working fine but at each boot i have the same message how can i solve this problem i tried a cmos with no result and in bios i didn't saw any option about fan?I wait an explanation from a member,,have a nice day (just to add i'm french so i hope my message will be understandable )😀 (before i change the cpu there was no error message during boot)

[itsmyname]

@pull-lift -- is there another fan (maybe on the back-panel) that is not spinning when the computer is powered-on? Is the cable from that fan NOT connected to the motherboard?

[pull-lift]

Hi there is the cpu's fan and the fan from the power supply,both are spinning during boot so i don't understand why the POST message is displayed?Have a nice day greetings.😊

[itsmyname]

@pull-lift -- it is the three-wire fans that provide feedback to the motherboard, indicating the speed (RPM) of the fan. Your computer probably has a two-wire fan inside the power-supply.  So, check your three-wire fan(s), to ensure that they are spinning fast-enough to avoid the error-message. Also, check the motherboard settings, to not try to monitor any non-installed fan.

[pull-lift · Accepted solution]

Hi i solved the problem with installing a fan with 4 pins on the motherboard at 25 connector named rear fan (marked A on the picture joined)and there is no more post message with fan error detection.I hope this will help someone who have this kind of problem.