Air Flow Sensor Potentiometer

Fig. 10 Special Tool 1348/1 Installation:

Note: As the potentiometer adjustment is very sensitive, a special tool is required to position the sensor plate accurately, and hold it steady. Using tool VW 1348/1, Fig. 10, is recommended. Do not attempt this adjustment without this tool or an equivalent.
1. Initial setup
a. Remove fuel pump fuse (number 13).
b. Remove intake air preheat control valve, and both hoses, from the air filter.
c. Remove the air flow sensor air boot.
d. Disconnect the fuel supply line at the fuel filter.
e. Remove air duct to the oil cooler.
f. Remove air filter housing from lower bracket (from under the car).
g. Disconnect the harness plug from the differential pressure regulator.
h. Push air flow sensor assembly away from the fender and lift up to gain access to the air flow sensor potentiometer.
2. Carefully remove the sealant from the potentiometer adjustment screw.

Fig. 8 Test Harness VW 1501:

Fig. 10 Special Tool 1348/1 Installation:

3. Connect test harness (VW 1501) Fig. 8, between the potentiometer and the injection harness plug.
4. Connect a voltmeter to terminals 2 and 3 on the test harness.
5. Install tool VW 1348/1, Fig. 10, as follows:
a. Pull the slide out to its upper stop.
b. Set the tool over the center of the sensor opening so that the pointer is towards the fuel distributor.
c. Push the slide down to the stop, then turn the center screw in until the magnet contacts the sensor plate mounting bolt.
6. Adjust the center screw of the sensor plate positioning tool until the output voltage is the same as it was in step 10 in the testing procedure (in "DIAGNOSIS AND TESTING").
7. Connect the voltmeter between terminals 1 and 3 of the test harness.

Fig. 16 Air Flow Meter Potentiometer Voltage Value Graph:

8. Adjust the potentiometer trim screw until voltage reading is within specification, Fig. 16.
9. If the voltage values cannot be adjusted to specification, remove the fuel distributor, and air filter housing, then replace the air flow sensor housing assembly. The potentiometer cannot be replaced separately.