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Home >> Honda >> 2012 >> Fit Base, Automatic Trans >> Repair and Diagnosis (Single Page) >> Accessories & Equipment >> Heated Glass/Defoggers >> Rear Window Defogger >> Function Test
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Function Test

NOTE:
  • Before testing, check the No. 10 (7.5 A) and No. 59 (20 A) [(30 A)], fuse in the under-dash fuse/relay box.
  • Aftermarket window tinting should be removed before testing.
  • Be careful not to scratch or damage the defogger wires with the tester probe.
  • When testing the defogger, hold a cup of hot steaming water near the glass. The steam can help diagnose a broken or under-performing defogger grid.

[ ]: With power mirror defogger

  1. Turn the ignition switch to ON (II), then turn the rear window defogger switch ON.
  2. Measure the voltage between rear window defogger A (1P) positive terminal and body ground. There should be battery voltage.
    • If there is no voltage, check for:
      • Faulty rear window defogger relay.
      • Faulty rear window defogger switch.
      • An open in the BLU wire to the positive terminal.
    • If there is battery voltage, go to step  3.
    Fig 1: Identifying Rear Window Defogger Battery Voltage Across Glass Graph
    G05960170Courtesy of AMERICAN HONDA MOTOR CO., INC.
  3. Measure the voltage between rear window defogger B (1P) negative terminal and body ground. There should be less than 0.2 V.

    If there is greater than 0.2 V, check for an open in the ground (BLK) wire or poor ground (G602). If there is 0.2 V or less, go to step 4.

  4. To avoid damaging the defogger grid, wrap a single strand of bare copper wire or aluminum foil around the voltmeter probe. Use the foil or wire as a contact brush when moving across the defogger grid.
    Fig 2: Wrapping A Single Strand Of Bare Copper Wire Or Aluminum Foil Around Voltmeter Probe
    G00509548Courtesy of AMERICAN HONDA MOTOR CO., INC.
  5. Touch the voltmeter positive probe along each defogger wire, and the negative probe to the negative terminal.
    NOTE: Touch the copper wire or aluminum foil wrapped around the probe, not the probe, to avoid damaging the defogger wires.
    • If the voltage is as specified, the defogger wire up to that point is OK.
    • If the voltage is not as specified, repair the defogger wire.
      • If it is more than specified at one of the points, there is a break in the negative half of the wire.
      • If it is less than specified at one of the points, there is a break in the positive half of the wire.
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