Last night after a serious thunderstorm, I drove my 2012 TSX Wagon w/ Tech to the end of the neighborhood to pick up dinner. About a mile from home, I drove through a shady patch and the headlights, set to 'auto,' turned on—normal behavior, but I twisted the switch on the left stalk to 'off' and when I did so, my windshield wipers turned on at high speed for about 3 swipes. I thought that was odd but wasn't really paying attention until I came to a stoplight a quarter mile further and they came on again, high speed, with the wiper switch still in the 'off' position. Then the windshield washer spray turned on; neither the wipers nor the spray reacted to any interaction with the right stalk and they would only stop when I turned off the ignition. When I started the car, they started again, so I turned toward home with wipers and washer spray going nuts in the broad daylight. On the short drive home I fiddled with the stalks again and at one point the wipers and spray turned off when I switched the headlights from 'off' to 'auto,' but that could be coincidence.

So I parked the car and left it for a few hours, came out later to find the left foglight on, and only that light, despite the car being off and the headlights set to 'auto;' the light eventually went off on its own, then came back on again, seemingly unrelated to any interaction on my part. Now I'm thinking it's not just a bad switch at the wipers, but some other electrical gremlin. So far, all affected features are connected to the driver side fuse box, but last night I checked both interior fuse boxes and the one under the hood and all seemed bone-dry (have not pulled the fuses yet to check but will today). Nothing inside the car was wet except a bit of condensation inside the windshield near the dash, probably because it was about 80* before it stormed.

I've left the car sitting overnight and now in the sun to hopefully dry it out in case something did get wet, but if I turn it on this afternoon to this same insanity, what can I do to troubleshoot before I have to give in and take it to the shop? I absolutely love this car, but I knew when I bought it that all the electronic baubles might bite me in the a**. Thanks in advance!

 

I would check the Automatic Lighting Sensor on top of the dash first. Also check the passenger's side fuse box, behind the kick panel, as the ALS routes through there.

I have a 2009 TSX electrical service manual if you want to me to look through it for anything.

 

Thank you! Since posting this, I did discover a leak on the driver's side, with water running down the wire bundles behind the fuesbox after heavy rain. The car has now been sitting with battery disconnected and under a car cover for several days, with a pantyhose filled with cat litter in the driver side floorboard to hopefully dry it out. I really hope nothing has shorted out.

Almost exactly a year ago, I had the windshield replaced at a local shop after it was broken by a flying piece of highway debris; the first glass company that the body shop contracted did a sh*t job, because the windshield came back with silicone gobbed sloppily all over the glass, then about a week later revealed a BAD leak on the passenger side of the windshield, like an inch of water pooled in the rubber floor mat bad. I sent it back and the shop kept it for over 2 weeks trying to pinpoint the leak before finally calling a second glass company, who tested the passenger side of the windshield and found the leak, then repaired it. It was a HUGE headache and I thought it was over, but now I'm thinking the whole windshield needs to be removed and replaced or re-set, because I'm betting that's where this new leak is coming from.

 

Ugh that stinks, but it does sound like the root cause of your electrical problems.