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Home >> Nissan-Datsun >> 1978 >> 280Z Automatic Trans >> Repair and Diagnosis >> Engine Performance >> Engine Control Systems >> Transmission Controlled Spark System >> Testing >> Top Gear Detecting Switch & Overdrive Detecting Switch >> 1979 Man. Trans. Equipped Models Only
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1979 Man. Trans. Equipped Models Only

  1. To test for proper on/off operation of top gear detecting switch and overdrive detecting switch, connect ohmmeter leads to detecting switch leads and shift transmission from 4th or 5th gear to other forward gears and check for continuity.
  2. The top gear or overdrive detecting switch is okay if ohmmeter shows continuity with transmission in 4th or 5th gear and no continuity with transmission in any other gear. If not, replace top gear or overdrive detecting switch.