Fan header sensor cutoff

I have a panaflo 92mm on a rheo. when i turn down the fan for silent mode, at about half way the ran sensor cuts out. this occures at about 2500 rpm according to fan speed. does anyone know why this is and if there is a work around to get sensor readings through my complete operating range?

Generally the fan speed is read with the use of a circuit that takes advantage of Hall effect sensors. My guess is that the circuit just can't read that low. Its unlikely that there is a worthwhile fix.

Moto7451 said:

Generally the fan speed is read with the use of a circuit that takes advantage of Hall effect sensors. My guess is that the circuit just can't read that low. Its unlikely that there is a worthwhile fix.

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would it work if PWM fan control is used? this is the only way i could see to fix this. but dont know if the pulsed power would screw up the sensor. so for those that use pwm fan controlers; do you get accurate fan speed sensing?