Veloster rain light sensor issue

I had a similar issue with my Veloster. The symptoms you are describing, especially the erratic light behavior paired with rain-sensing issues, point towards a common problem, but it requires some terminology explaining beforehand. Your car's rain sensor utilizes infrared light. The sensor emits a beam of infrared light onto the windshield. When the windshield is dry, most of the light is reflected back into the sensor. However, when water droplets are present, they cause the infrared light to scatter, and less light is reflected back. The sensor then interprets this change in reflection as the presence of rain and activates the wipers.

Whoa, technical! So, if light isn't bouncing back right, what's the culprit? Is the sensor itself toast, or are we talking wiring gremlins? Tell me more!

Usually, what happens is that tiny air bubbles form under the gel pad of the sensor, the interface between the sensor and the windshield. Those bubbles mess with the refraction enough to cause a fault. Now, I am not saying you should not check your connections, but everything you said points to the sensor being faulty. It is probably best to have a workshop inspect it. It could be that the sensor is failing, or that the windshield is not clean, or that there is damage to the windshield.

The Veloster went to the shop and turns out, the gel pad was bubbled up like crazy. New pad, sensor recalibrated, and all systems are go. Cost me 62€, which isn't too bad considering the headache it was causing. Thanks a million for the help!