Function Test

NOTE:

Before testing, make sure the No. 4 (40 A) fuse in the under-hood fuse/relay box and the No. 16 (7.5 A) fuse in the driver's under-dash fuse/relay box are OK.
Aftermarket window tinting should be removed before testing.
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.
Be careful not to scratch or damage the defogger wires with the tester probe.

Turn the ignition switch to ON (II), or press the engine start/stop button to select the ON mode, then turn the rear window defogger switch ON.
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 climate control switch.
  - Faulty gauge antenna coil.
  - An open or high resistance in the GRN or WHT wire to the positive terminal.
- If there is battery voltage, go to step 3.
Fig 1: Identifying Rear Window Defogger A (1P) Positive Terminal And Rear Window Defogger B (1P) Negative Terminal
Courtesy of AMERICAN HONDA MOTOR CO., INC.
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 (G801). If there is 0.2 V or less, go to step 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 Single Strand Of Bare Copper Wire Or Aluminum Foil Around Voltmeter Probe
Courtesy of AMERICAN HONDA MOTOR CO., INC.
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 voltage is more than specified at one of the points, there is a break or high resistance toward the negative half of the wire.
If voltage is less than specified at one of the points, there is a break or high resistance toward the positive half of the wire.