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Discussion Starter #1
Does anyone know the pinout of the rain sensor that was included with the 2003-2006 MDX? (part number 38970-S3V-A014-M1, if I'm not mistaken)

The wire colors on mine are as follows: Green, Blue/White, Black/Yellow, Green/Yellow, Yellow, Black (ground), Red, Green/Red.
 

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Here is the relevant part of the troubleshooting for the sensor.

FWIW, I had a rain sensor issue with my 2006 Audi A3, and could find NOTHING on how it was tested / configured - anywhere! Have to love the MDX forum for this kind of thing (and the availability of actual information from Honda).

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Discussion Starter #5
Any idea why, during constant rain, the sensor starts by running wipers with a two-second delay, moves to a one-second delay, and then runs them constantly for a few seconds? Shouldn't the delay be consistent during constant rain?
 

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Sounds like it could just be the logic that Honda coded into the controller - it would make sense that the auto wipers would start slowly, and then reassess every swipe or two to see if it needs to ramp the speed / frequency of the wipers up a notch (or not).
 

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Discussion Starter #8 (Edited)
But sometimes it happens during light rain... Worth mentioning that I retrofitted this sensor into a Civic.

Is it possible that I still have air bubbles in the sensor that are being interpreted as rain?
 

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It's possible. My MDX didn't have auto wipers, but I did have an Audi that did, and replaced the silicon pad that holds the sensor to the windshield. It's got to be really, really well-seated and devoid of bubbles to work correctly. IIRC, I got a replacement from Amazon in a day or two for under $10.
 

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Discussion Starter #10 (Edited)
Something else just occurred to me. There are two wires that "should have battery voltage" at all times, red and yellow. Is one of them +12V and the other -12V? Because this thing is looking for not only rain but changes in rain as well, and if it's using an analog differentiator, it needs both polarities to work properly. Also, the "LO" setting wire alternates between +12V and -12V according to that page, which would further justify the need for a -12V supply.

Edit: Come to think of it, it has to be using an integrator, right? That would also require both polarities.
 
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