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Home >> Mercedes Benz >> 1975 >> 280 >> Repair and Diagnosis (Single Page) >> Engine Performance >> Engine Control Systems >> Exhaust Emissions System - Exhaust Gas RECIRCULATION >> Testing >> Switchover Valve >> 1975-76 280 Models
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1975-76 280 Models

  1. Disconnect relay box and connect terminals No. 3 and 4 with jumper wire. Turn ignition on. The EGR switchover valve should click. If EGR switchover valve is functional, check starter lockout and back-up light switch.
  2. Disconnect relay box and connect a voltmeter between terminals No. 2 and 5. Turn ignition on. With transmission in Park or Neutral, voltmeter should read battery voltage. If voltage does not exist, replace relay box.