Van or Flap air flow sensor/meter (AFM)

How Van  air flow meter work

The van air flow sensor is located ahead of the throttle and air fllow meter in vehicle measure the quantity of air which going into the internal combustion engine. the spering loaded mechnical flap . The flap is pushed open by an amount that is proportional to the valum of air enterning the engine.
The flap has a wiper arm that rotats against a sealed potiontion meter (varaible resistor or rohastate) alowing the sensor output voltage to change acording to air flow.
The greater the airflow the futher the flap is forced open this lowers potentionmeter resitance and increse the voltage return signal to the computer.
The ECU calculate how much fuel is needed to inject into cylender port.

Diagnosis or check Van Air flow
Check a van air flow sensor by using a multimeter to check voltage out and resistance valve between the sensor various terminal.
Sensor out put voltage should rise from around 0.25 volts to about 4.5 volts .
The flap goese from close to open here is my meter reading.

VAN ANGLE	VOLTAGE OUT
0	1.17 volts
30	1.72 volts
45	2.12  volts
60	3.03 volts
90	4.02 volts
Full open	4.62 v0lts

Plot of results on below graph

the results get manufactures specification because i had explane obove the output voltage open from 0.25 v to close 4.5 v in also my reading in close 4.21v and full open 0.42v .