BYD Seagull Windscreen Demist Turns On the A/C: Normal?

BYD Seagull demist turns on the A/C: the compressor running isn't a fault

Scope: China-mainland 2026 Seagull; official website file 260317; PDF pp. 288–289, "Air conditioning system"

What demisting is designed to do

The manual explains that when front windscreen defrost/demist is switched on, the air conditioning also comes on, regardless of whether you previously used the compressor button. Seeing the A/C start during heating or demisting is not evidence that the system is out of control. To judge whether something is wrong, first confirm whether you are in normal ventilation, cooling or windscreen demisting. ^[1]

Judge comfort and visibility separately

A warm cabin does not mean the glass is clear. The manual also notes that using the compressor while heating reduces moisture in the airflow, and that long periods of recirculation can increase the risk of misting. Owners can adjust normal air conditioning functions as the manual describes, but should not switch off necessary demisting to save energy and carry on driving with obstructed visibility. ^[1]

Describe the result when reporting a fault

When reporting a problem, saying whether air is blowing onto the glass, whether the mist clears and whether normal air conditioning is also affected is clearer than just saying the compressor is always on. If you cannot keep a clear view, stop safely; persistent lack of effective airflow or unusual smells should be checked by a workshop. This article gives no refrigerant charging, compressor or high-voltage circuit repair steps. ^[1]

Sources

[Source 1] BYD China official website: 2026 Seagull Owner's Manual (in Chinese) (public PDF on the official website)
https://www.byd.com/material/domestic-official/user-manual/ocean/2026%E6%AC%BE%E6%B5%B7%E9%B8%A5%E7%94%A8%E6%88%B7%E6%89%8B%E5%86%8C260317.pdf
Verified: 2026-10-03; page publication date not confirmed.

This article contains information-organising suggestions from the editorial team; it is not a manufacturer repair procedure.