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Home >> BMW >> 1979 >> 633CSi Automatic Trans >> Repair and Diagnosis >> Engine Performance >> Engine Control Systems >> Air Injection System >> Testing >> Electromagnetic Switch & Speed Switch >> 633CSi & 733i
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633CSi & 733i

  1. With engine at idle, disconnect electrical connector from electromagnetic switch (with Blue cap). Connect a test lamp between connector terminals. Test lamp should not come on. If test lamp comes on, speed switch is defective.
  2. Next, increase engine speed. Test lamp should come on when engine speed reaches approximately 3750 RPM. If not, connect test lamp directly to ground.
  3. If test lamp now lights, power supply line to switching valve is not grounded. Repair as necessary and retest. If lamp still does not come on, speed switch is defective.
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