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2009 Honda Pilot Rear Defrost through A13 - Light green wire at back of switch module?

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I used wirecolor.com to identify rear defrost line (light green at control module in dash). I found the wire at the connector behind the switch cluster and confirmed green wire floats high when rear defrsot is OFF and is 18mV when defrost is ON. Assuming this is the correct wire, a pulse low (or constant ground) does not seem to trigger the defrost cycle. Can you provide any additional detail on the wiring? Thanks.
asked Nov 14, 2018 in Honda by Ron Tang (230 points)

1 Answer

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Best answer
The light green wire must be latched to ground to trigger the defrost relay. It is possible that the light on the defrost button does not turn on when triggering. Put light green to ground, wait 1 minute and touch the rear glass.

Make sure you have 12v at switch on yellow wire.
answered Nov 14, 2018 by Mathieu Bertrand Collin (51,270 points)
selected Nov 15, 2018 by Ron Tang

I was touching the heated mirrors and they were not heating up when latching the green to ground. I didn't go around to the back glass blush. Do you know if the circuits are tied together or isolated? Both mirrors and back glass get warm when activated at the switch.

Mirrors are controlled over data, you would need to run wires to each doors to activate heated mirrors.... much bigger job.
Perfect! Thanks for the information. I will wire up the green to yellow/black, program Function 25 to Mode 6, and Function 39 to Mode 2, and skip the mirrors... for now.
Hopefully someone else will find this helpful - I programmed the remote start to trigger the rear defrost circuit below 5c as per above. I did not proceed with running the additional wires to each individual heated mirror. As the temperature dropped below 5c, the rear defrost would turn on when remote started and it works as intended. This week the temperature dropped to -4c with significant frost forming on the car and the mirrors. To my surprise, the mirrors are also now warming up and defrosting! As mentioned above by Mathieu, the mirrors are controlled over the canbus data and at the time of installation, grounding the green wire would only warm the back glass. It appears there is software in the car that triggers the heated mirrors in addition when the temperature drops below another threshold. I don't know what temp that would be, but suffcie to say, there is no need to run additonal wires to each mirror. Just connect the light green and the mirrors will heat when the temp drops!
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