What is the square wave button next to the AC?
3 Answers
The square wave button next to the AC is the defogging and heating function button. Here are the relevant introductions: Introduction 1: There are generally two defogging buttons in a car, one is the front windshield defogging button, usually marked with a fan shape and a wave line, and the other is the rear windshield defogging button, usually marked with a square and a wave line. Introduction 2: The front windshield defogging relies on the air conditioning system, with dedicated air vents located near the front windshield on the center console. The rear windshield defogging mainly uses electric heating wires. After turning on the rear windshield defogging switch, the heating wires will generate heat, thereby achieving the purpose of helping to defog.
That button with a square and a wavy arrow is the air recirculation mode switch. I remember testing it specifically on the highway last week—when turned on, it stops drawing air from outside and instead circulates the air inside the cabin. This is especially useful when driving through tunnels or behind trucks with strong exhaust fumes, as it prevents odors from entering the cockpit. But be aware that prolonged use can cause the windows to fog up, particularly in winter when the heater is on, as moisture can’t escape. Nowadays, I use recirculation mode in traffic and switch to fresh air mode on the highway, balancing air freshness and fuel efficiency. The manual mentions that some models can sync this with automatic climate control, but my older car doesn’t have that advanced feature.
This is the recirculation button, which I usually refer to as the cabin air recirculation button. I press it every time I pass a garbage truck or on smoggy days, and I can clearly feel the reduction of dust inside the car. Last time when I took my child to the hospital, the pediatrician specifically mentioned that this mode is very helpful for people with allergies. However, once I forgot to turn it off during a two-hour long drive, and I felt dizzy when I got out of the car, probably due to the high carbon dioxide concentration. Now I treat it as a temporary protective switch, usually turning it on for about twenty minutes before switching back to auto mode, which is both comfortable and safe.
