EVO 212 CPU fan replacement

[#1]

A few weeks ago my PC's CPU was reporting a temperature of 65C. I guessed it would be the fan and it was. Even after a good clean it refused to move!

Needing the use of the PC it seemed that any 10cm fan would suffice and rushed to PC world and got a dual pack. Replacing the CPU fan was a doddle except the replacement only had three pins to connect to the power while the original had four. This meant I had to plug it into a different power port and the monitor software doesn't report the speed.

I added the second fan as an extra that also blows air over the CPU and is extracted by another fan at the front of the case.

Now, all seems well with the CPU temp regularly staying between 48 and 53C except on very heavy loads but the highest so far is 58C. The MB is a stable 35C. Would it be advisable to get the proper 4 pin fan or would the setup I have suffice?

Also, since adding the other fan to it's own power supply both the CHA_FAN3 and PWR_FAN frequently show 675000rpm before reverting back to around 1500 within a second or two. Is this a symptom of something else? The fans carry on working during those couple of seconds.

[#2]

Fans make noise.  Lots of fans make more noise. Fans running full-on make more noise.  If you don't mind the noise then there is nothing wrong with the arrangement you have.  See here for what the fourth pin does for you: 

https://www.howtogeek.com/275339/how-to-auto-control-your-pcs-fans-for-cool-quiet-operation/

[#3]

@ReedRichards

Thanks for the link

[#4]

@ReedRichards

Thanks for the info and link.

Currently have a message on screen showing the MB temperature is -128C where the Sensor App is showing it at 35C.

Can anyone shed some light on why I now get the anomalous displays (as in post#2 as well)?

[#5]

Have you tried identifying the cause by unplugging each fan in turn temporarily?

Have you tried resetting the BIOS to default to see what happens?

[#6]

I'm going to leave as is for now. Next time I open the case (I want to take out the DVD Writer) I'll have a further check.

Thanks all.