Prado: Turn Signal & Alternator Fixed by Fuse Replacement

Toyota Prado 120 Series
1

This document outlines troubleshooting steps for diagnosing and resolving indicator/turn signal problems and a non-charging alternator in a Prado vehicle.

Problem

The vehicle experienced a complete loss of indicator/turn signal function and the alternator was not charging the battery.

Solution

The primary cause was a blown 10A fuse (IG1 No.2) in the driver’s side fuse box. Replacing this fuse restored both indicator functionality and alternator charging.

Relevant Parts and Locations

  • 10A Fuse (IG1 No.2): Located in the driver’s side fuse box.
  • Flasher Unit: Located behind the main fuse panel under the dash. Access requires loosening the fuse panel.
  • ALT-S Fuse: Located in the engine bay fuse box; check if the alternator is not charging.

Troubleshooting Steps

  1. Initial Checks:
    • Verify hazard lights are functional. If so, all bulbs are likely good.
    • Check the “HAZ/Turn” fuse under the bonnet.
  2. Flasher Unit Diagnosis (If Indicators Still Don’t Work):
    • Locate the flasher unit by listening for the clicking sound when hazard lights are activated.
    • Consider testing the continuity of the wiring between the indicator stalk and the flasher unit, specifically the Green/Black and Green/Yellow wires.
    • Check the white/black wire from the steering column to the indicator stalk for a good earth connection.
  3. Alternator Not Charging Diagnosis
    • Measure battery voltage with the engine off and running. A healthy charging system should show a higher voltage when the engine is running.
    • Check the ALT-S fuse in the engine bay.
    • Check the plug into the back of the alternator.
    • Crucially, inspect and replace the 10A “IG1 No.2” fuse in the driver’s side fuse box. The alternator and indicator circuits are supplied from this fuse.
    • If other dashboard warning lights are not working, check the 7.5A “Gauge” fuse.

Notes

  • The trailer wiring harness has a separate flasher relay.
  • The indicator stalk assembly is a non-rotational design, so a faulty clock spring is unlikely.

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