Long story short - I got a rock crack in my windshield. Glass shop replaced the windshield, but there was a leak into the rain sensor. New windshield, new sensor, won't work. It will occasionally wipe intermittently when on the sensor position, but definitely not how it's supposed to. Took it into the dealer and among other things over the past few months, my light bar (aftermarket - wired to the high beam hot lead) stopped working.

Dealer says the light bar may have damaged the wiring, possibly up into the BCM and damaged it, since programming and replacing the wiper sensor is all a no-go. Is the BCM prone to causing multiple faults when it gets damaged, or is the explanation likely somewhere else? It seems odd that the light bar was still working fine for several months while the wipers were not.

 

I had my cracked windshield replaced by safelite with their house brand windshield, and experienced the same type of intermittent and erratic wiping in the rain sensor position. Had them replace the windshield again on their dime, since they verified that the rain sensor was working properly before they did the first replacement. The second replacement windshield was even worse than the first - the wiper refused to work at all in the rain sensor position. Safelite refused to replace the windshield again, and claimed that it was a sensor issue and to bring it into MINI for diagnosis and repair, which I did not do, as I fully expected MINI to tell me that the windshield should have been replaced with an OEM MINI windshield. I ended up pulling the fuse for the rain sensor, which renders the rain sensor mode into a one-speed intermittent mode. (It also disables the auto lights, but that wasn't an issue for me.)

Lesson learned: OEM MINI replacement windshields only.

 

So are you actually sure the problem is the windshield? Because Safelite is actually paying for the rain sensor issue. They replaced my windshield three times with two different brands before swapping the sensor.

 

Am I 100% sure? No, unless I bring it in to MINI and pay a diagnostic fee. All I am sure of is that is was working perfectly right up until they removed the original windshield, as it was lightly raining on that day. Could they have damaged the sensor during removal and reinstallation? Possibly. Did they end up replacing it with an OEM MINI windshield?

 

So they were initially convinced it was the BCM since they swapped it with a known good one and no workey.

But then they noticed a bubble in the windshield RIGHT over the sensor, so they think the windshield is the problem. I feel bad for Safelite, they've always done a great job with my cars in the past, and they replaced the windshield THREE times in my car, as well as replaced my rain sensor, all happily and without complaint. But the dealer is going to work with them on swapping the windshield again with a MINI one under warranty before they go into the BCM. I'll update when I know for sure.