Checking the vacuum and atmospheric valves (BMW 5 Series E12)

This check is carried out in the same way as on the removed throttle servo drive of the 1st chamber (see above).

Potentiometer check

Connect the tester (in ohmmeter mode) to the plugs "4" and "5" of the servo connector and measure the total resistance of the potentiometer, which should be within 1.4-2.6 kOhm.

Connect the tester to the plugs "4" and "7" of the servo connector. Applying vacuum with a vacuum pump, slowly and completely push the servo pusher in, while measuring the resistance: it should constantly decrease from 0.9-1.9 kOhm to 500 Ohm.

If the resistance value is not within the specified limits, replace the servo.