What are car rearview mirrors?
The car rearview mirror is actually what we commonly refer to as the rearview mirror. It is a safety device on the car used to observe the rear and side road conditions, serving as the driver's "third eye".
What makes the mirrors different?
The internal rearview mirror mostly uses a plane mirror, which provides a true and undistorted image and can accurately reflect the distance behind the car; the external rearview mirror commonly uses a convex mirror, which offers a wider field of vision but the image will be reduced and distorted, eliminating blind spots.
Where are the mirrors installed?
They are mainly divided into three categories: the internal rearview mirror is installed above the front windshield inside the car to view the rear directly; the external rearview mirror is on the sides of the car doors to view the side rear; the lower rearview mirror is to observe the front lower road conditions.
Why are there differences in names?
It's fine to say "reflective mirror" in daily life, but professionally, the more accurate term is "rearview mirror" because reflective mirrors generally refer to all mirrors that reflect light, while rearview mirrors have specific automotive safety standards.
The core function of the car rearview mirror is to help the driver see the road conditions behind and on both sides clearly, expanding the field of vision to eliminate visual blind spots, making maneuvers such as changing lanes, overtaking, and reversing safer.
How do the mirrors divide their functions?
The internal rearview mirror mostly uses a plane mirror, which can accurately represent the actual distance and size of the vehicles behind, allowing the driver to accurately judge the following distance.
The external rearview mirror commonly uses a convex mirror, which expands the field of vision to more than twice the original size using the spherical reflection property, although the image will be reduced and distorted, it can cover more areas on the side rear.
The lower rearview mirror also uses a convex mirror, specifically to observe the road conditions on the front side below the vehicle, preventing obstacles or pedestrians from being in the way when starting.
How to use the mirrors while driving?
Before changing lanes, look in the external rearview mirror to confirm if there are any vehicles coming from the side lane, then turn your head to check the blind area to confirm safety.
When reversing, use them in combination: the internal rearview mirror views the rear directly, the external rearview mirror views the sides, and the lower rearview mirror views the area around the wheels. Check the environment from all angles.
When turning, use the convex mirror in the emergency area to reflect the vehicle dynamics on the other side of the bend to the field of vision in advance, allowing both parties to predict the road conditions.
What are the upgrade functions?
Electric heating and de-icing: in rainy or winter conditions, it can quickly remove water vapor and frost on the mirror surface to ensure clear vision.
Automatic anti-glare: in high-end models, it can automatically adjust the mirror reflection rate based on the intensity of the light from behind to reduce night-time glare interference.
Automatic folding: when parking, the mirror surface can automatically retract to avoid scratches, improving usability.
How to identify the core faults?
First, distinguish between three types of faults: electric folding/adjustment failure, mirror damage, or shaft fracture. The core troubleshooting sequence is: check the settings and power supply → test mechanical jamming → diagnose circuits/motors. Most non-hardware damage issues can be resolved by self-resetting.
Core fault types and quick self-checks:
- The mirror does not automatically fold/expand: 90% of the time, it is due to the switch not being turned on, low battery protection, or temporary logic deadlock; prioritize checking the "lock car automatic folding" switch in the central control, long-pressing the remote lock key, restarting the vehicle, or disconnecting the negative terminal for 30 seconds.
- Unable to electrically adjust the angle: mostly due to damaged adjustment switch, blown fuse, or internal motor failure; try switching the L/R position to listen for the motor sound; if there is no sound, check the fuse box corresponding fuse.
- Mirror breakage or shaft fracture: only the mirror glass needs to be replaced (requires special glue/clip); shaft breakage or shell cracking requires replacing the assembly; in an emergency, you can temporarily fix it with AB glue but do not rely on it for a long time.
- Single-sided failure or abnormal noise and jamming: single-sided motor/gear damage or foreign object freezing and jamming; in winter, warm the vehicle to melt ice, if there is a "clicking" idle sound, it is mostly gear wear, and it needs to be disassembled and repaired for replacement. Enter the vehicle menu and confirm that "Automatic folding when locking" and "Automatic unfolding when unlocking" are checked; for some German cars, you need to long press the remote lock button to trigger.
Check the battery voltage. When the battery is low, the system will disable the high-power folding function; after power loss, you need to manually press the folding button to reset the memory.
Restart the vehicle or disconnect the negative battery terminal for 30 seconds and reconnect it to eliminate occasional system crashes of the control module.
Step 2: Mechanical and physical inspection
Observe whether there is mud, ice, snow or foreign objects blocking the gap of the rotating shaft; in cold weather, it is strictly prohibited to forcibly twist it; you should first warm the air conditioning to melt it before operating.
Gently push the mirror arm to feel the resistance: if it is completely stuck and there is no motor sound, it may be a gear misalignment; if the motor makes a sound but does not move, it is mostly due to damage to the transmission mechanism.
Do not forcibly fold or unfold under freezing conditions or with obvious resistance; it is very likely to burn out the motor or break the gears.
Step 3: Circuit and component diagnosis
Check the door panel switch and fuse box on the driver's side (refer to the manual to locate the specific fuse for the rearview mirror).
If there is a single-sided fault and the motor makes a "buzzing" sound but does not move, it is mostly due to damage to the motor or gear set on that side; if there is no response at all, check if the wire harness plug is oxidized and loose (commonly found at the door hinge).
Use an OBD diagnostic tool to read the BCM (body control module) fault codes to accurately locate motor overload or sensor abnormalities.
Maintenance decisions and costs reference
No repair scenarios: Settings closed, temporary logical conflicts, slight sticking reset to normal.
Self-replacement: Only if the mirror lens is broken, you can purchase the corresponding model of glass and stick it yourself (costs several dozen yuan), make sure it is flat without bubbles.
Professional repair: Motor/gear damage, wire harness short circuit, shell fracture require replacement of the assembly or disassembly for repair.
If the vehicle is still within the warranty period, non-human damage can apply for compensation.
Warning: When involving circuit disassembly, motor replacement or structural fracture, it is recommended to handle it at an authorized service center to avoid waterproof failure or secondary damage; if the mirror lens loosens and falls off while driving, stop immediately for handling to prevent the obstruction of vision and causing an accident.
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