Part 2 — The Air Dryer Clue The real clue came from the air system. The air dryer had already been replaced more than once. The problem was that the air dryer heater was not working properly, and at one point there was no air coming out to the secondary side. Water had gotten into the air tanks. That matters because water in the air system does not just stay in one place. It can travel through the brake air system and damage or contaminate valves, fittings, modulators, and sensors. The strange part was that every time the air dryer purged, the warning lights could trigger. Rain and wet weather made it worse. After a full regen, the problem would sometimes go away for a few days, probably because heat dried out moisture around the system. That pointed more toward moisture, air system contamination, wiring, or ABS components — not just a bad radar.