Mercedes-Benz W201 airflow meter potentiometer
W201: how does the airflow meter potentiometer affect running?
The potentiometer tells the control unit the position of the air flap plate. When its track wears or gets dirty, the voltage fluctuates and the car jerks, idles unevenly or may stall under load. The track can be cleaned lightly with contact cleaner, but it must not be bent.
W201: how do I test the airflow meter potentiometer?
Measure the resistance with a multimeter between the middle and top pins of the 3-pin connector while slowly pressing the plate down. The resistance must increase smoothly without breaks. If the meter shows OL or the reading jumps about, the carbon track is broken or dirty and the potentiometer must be cleaned or replaced.
W201: what is the correct potentiometer voltage at idle?
At warm idle, the voltage between the middle and outermost terminals should be about 0.70 V. The adjustment is precise, and tightening the screws changes the value, so check the reading again after tightening. If the value will not settle, also check that the potentiometer and throttle body connectors have not been swapped with each other.