RPM always 0, fan runs at max

[mcdjork]

I've built the board, but trying to figure out why the fan always runs at max--even when first powering on the machine. The fan is the same Delta model you used, and I have used the appropriate wiring and code. The temperature is reading correctly. As expected, it differs from the nvidia-smi readout, but it also never really has a chance to elevate much, as the fan is keeping the gpu relatively cool. Here is the output:

gpu idle:
temp=29.87 PWM%=19 RPM=0
temp=29.87 PWM%=19 RPM=0
temp=29.81 PWM%=19 RPM=0

in use:
temp=33.19 PWM%=22 RPM=0
temp=33.13 PWM%=22 RPM=0
temp=33.19 PWM%=22 RPM=0

[askanier]

Hi! Pin 2 is not connected with the delta fan. This pin reads the tacho signal and
rpm is calculated by the pulse time of this signal. So rpm is "0"

time = pulseIn(2, HIGH);
rpm = (1000000 * 60) / (time * 4);

Can you check the output of pwm pin 3? For example by an oscilloscope?