How to troubleshoot an electronic clutch fan circuit on an Olds Bravada or Chevy Blazer with a 4.2L engine. This clutch fan has 5 wires. (2) output control (3) speed sensor input (hall effect design)

Engine Performance Diagnostics

Topics discussed


  • check engine light (P1482 Cooling Fan Speed Sensor Circuit)
  • noisy fan


  • replace blown fuse for the electro viscous fan

test shown

  • how to test the computers output control of the fan circuit
  • how to test the fan speed sensor circuit
  • how to identify power and ground side switching
  • how to determine signal circuit design (pull-up or pull-down)

Tools used

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HVAC and Cooling systems troubleshooting

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For more information on this topic, I have written a “field manual” called Engine Performance Diagnostics which is available as an eBook or paper book.

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