Component Testing: Potentiometer
- Ensure engine is at normal operating temperature. Connect Test Adapter (VW1501
) between potentiometer and harness. See Fig 1
. Connect multimeter to test adapter connectors 1 and 3. Switch multimeter to DC volts scale and turn on ignition. Reading should be 4.35-5.35 volts.
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- Switch multimeter leads to test connectors 2 and 3. Start engine and let idle. Engine cooling fan must not come on during this test. Reading should be .4-.9 volt. If reading is slightly outside tolerance, correct by adjusting the potentiometer trim screw. If correction is not possible, replace potentiometer.
- When replacing potentiometer, do not touch resistance strip or contact whiskers inside potentiometer. Loosely install potentiometer. Connect multimeter to test adapter connectors 2 and 3. Turn on ignition and measure voltage. Reading should be 10-100 mV. Adjust potentiometer to read correctly by turning trim screw.
- Pull adjusting slide on Sensor Plate Gauge (VW1348/1
) up to upper stop. Place gauge centrally on edge of airflow sensor with edge No. 3 pointing toward fuel distributor. See Fig 2
. Push adjusting slide down to stop. Rotate setting screw until base of magnet contacts sensor plate mounting screw.
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- Pull adjusting slide up to first stop (idle position). Adjust potentiometer set screw to obtain .5-.8 volt.
- Remove sensor plate gauge and install intake air boot. Start and run engine until cooling fan has cycled at least once. DO NOT
take voltage readings while engine is running.
- Stop engine and turn on ignition. Potentiometer voltage should be .4-.9 volt. If voltage reading is out of range, refer to step 2) for procedure. If you have performed all of these procedures and still cannot obtain correct voltage readings, replace airflow sensor.