What are the causes of water ingress on one side of the car cabin?

[DelJames]

Water ingress into the car cabin can occur due to the following reasons: 1. Sealing issues: Improper alignment of the sunroof cover, such as uneven height or incorrect left-right gaps that do not meet the manufacturer's standards, can lead to poor sealing. Additionally, if the sunroof cover is not fully closed or left open, it can cause water leakage into the cabin ceiling. 2. Corrosion problems: After collision repairs to the car roof, if proper rustproofing is not done, severe corrosion of the roof panel or the edges of the sunroof frame can result in water leakage into the cabin ceiling. 3. Sunroof drainage system issues: The sunroof drainage system mainly consists of drainage channels, drainage pipes, and drain valves. The sunroof is not completely sealed, allowing some water to seep in, which flows into the drainage channels. While minor water seepage is normal, problems such as cracked drainage channels, detached, folded, broken, twisted, or poorly routed drainage pipes, or clogged drain valves can all lead to water leakage into the cabin ceiling.