Fan 1 reported failed on NV+. Do I need a PWM 4-pin replacement fan?

Hello,

I have an NV+ (older one - I believe it uses a Sparc).  I'm getting notificatinons that Fan 1 has failed.  It doesn't look like it has failed - as it is still spinning, but it does show 0 rpm on the dashboard.  So perhaps the sensor is gone.  When I recalibrate, it comes back momentarily - but then goes back to zero. 

So my question - do I need a 3 or 4 pin (PWN) fan to replace this with?  I believe it is a 92mm fan and i've seen the Noctua NF-B9 is a popular choice, but it comes in a standard model and a PWM model.  Seeing as how the NV+ can slow down the fan speed depending on need, does it need a 4-pin PWM fan?

Thanks in advance.