How should air conditioning or heating vents be used during replacement to prevent condensation or fogging?

• A. Keep interior temp controlled to avoid excess moisture, and ensure interior surfaces are dry before curing; use HVAC to minimize moisture.
• B. Turn off HVAC completely.
• C. Use only heating.
• D. Use a separate dehumidifier outside of the vehicle.

Answer: (A)

Keeping the cabin environment under control is essential to prevent condensation and fogging during windshield replacement. Condensation happens when humid interior air cools on the inside surface of the glass, so maintaining a steady interior temperature and ensuring all interior surfaces are dry helps keep the dew point down and the bond area dry for proper curing. Using the HVAC system to remove moisture from the cabin air and keep surfaces warm enough to dry any dampness reduces fogging and supports a strong adhesive bond. Turning the HVAC off lets humidity linger and temperatures wander, increasing the chance of condensation. Relying on heating alone won’t reliably reduce interior humidity, and a separate dehumidifier outside the vehicle can’t affect the interior environment during the install.