What is the reason for the continuous noise from the rearview mirror motor?
3 Answers
The reasons for the continuous noise from the rearview mirror motor are as follows: Foreign object at the rearview mirror lens: If the car's rearview mirror is of the electric folding type, check if there is any foreign object between the mirror lens and the base. Remove the foreign object if present. Missing waveform or reversed wiring: Turn on the power supply of the motor's electronic control system and connect an oscilloscope to check if the waveform is missing any peaks. Missing phases can cause vibration and noise. Also, check if the compensation coil and armature leads are connected correctly. Magnetic circuit too strong: A magnetic circuit that is too strong can cause electromagnetic noise. Run the motor at its rated speed to see if the noise occurs only within a certain range. Then, cut off the power supply (both the armature and the excitation simultaneously) and observe if the noise persists during deceleration. If the noise disappears, it can be confirmed that the issue is due to electromagnetic noise.
My car has had this issue before. There are generally several common reasons for the rearview mirror motor to keep making noise. The motor may be aging internally or have dust inside, causing the bearings to wear and produce a rattling sound; if the gear system lacks lubrication or has foreign objects stuck, it can also cause continuous friction noise; issues with the wiring, such as loose wires or unstable voltage, may cause the motor to operate abnormally and produce a humming sound. More seriously, a faulty control module or signal interference can cause the motor to repeatedly start and stop. Don’t ignore it—over time, it may burn out the motor or affect mirror adjustment, compromising driving safety. It’s recommended to visit a professional auto shop as soon as possible. Replacing the motor or cleaning the gears isn’t costly, but delaying repairs can worsen the problem, such as making it harder to fix if water gets in during rainy weather. You can try turning off the power for a few minutes and restarting it first—sometimes this provides temporary relief—but ultimately, a professional diagnosis is needed.
I've repaired many similar cases where rearview mirror motor noise often stems from mechanical issues or electrical interference. Gear wear is the primary cause, as dried-up lubricant over time increases friction noise; foreign objects like sand stuck in the drive mechanism can also cause persistent noise; loose wiring connections or power fluctuations may make the motor hum or operate intermittently. Control switch problems are also common, where poor button contact keeps the motor running continuously. While this doesn't affect driving, it can be distracting and may damage the entire mirror system, increasing repair costs. Simple checks include shaking the mirror to check for stiffness, but it's best to have a shop test the circuit with a multimeter. Regular maintenance like monthly checks to ensure smooth operation and cleaning the mechanism can prevent issues.
