Have to reset CMOS every time, before PC will boot

[majestic4000]

I need to reset cmos every time before startup otherwise the pc will show black screen.This started happening after I replaced the cpu fan.No other changes where made to the system

the cpu is an amd a8 3850 and the motherboard ia an asrock a75-hvs

 

[jojesa]

I need to reset cmos every time before startup otherwise the pc will show black screen.This started happening after I replaced the cpu fan.No other changes where made to the system

the cpu is an amd a8 3850 and the motherboard ia an asrock a75-hvs

Did you just replace the fan or the heatsink/fan unit?
Which unit did you get? Does it has a 3-pin or 4-pin connector?