To understand a windscreen that takes too long to demist, compare it under normal, safe conditions: cold versus warm, idle versus steady speed, and light versus higher load. Record outside humidity, passenger load, and whether the A/C and fresh-air settings work. Change one condition at a time so the result stays useful.
Do not create a risky test just to reproduce it. Check the cabin filter and use the manual’s demist settings; avoid recirculation if it worsens fogging.
Quick educational note
For information, not a diagnosis or repair instruction. Vehicle-specific checks are still required. Consult the manufacturer's guidance and a qualified technician.
How to use this information
This article explains general principles and does not establish what is wrong with your vehicle. Read the content limitations.