Dell Inspiron 660S CPU fan is spining at full speed non stop when the PC is power off and before switching ON.

Dear Sir / Madam,

My Delll Inspiron 660S has a CPU fan issue. The fan is spinning to full speed when it is power off. At the same time, when I tun on the main power supply but before pressing the ON button, the fan is spinning at its full speed non stop . It can only returns to normal speed when it is fully ON.  I have changed a new CPU fan, checking the cable / power supply connections at the motherboard but could not fix the issue. Is this a motherboard temperature sensor issue that is difficult to fix? Is there any Dell  software utility that could help to fix this issue?

Thank you

Best Regards

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