What is the REM wire in audio systems?
4 Answers
REM in audio systems refers to the speaker control wire, which is connected to the position where the car ignition key is turned on. Here are the details about REM: Installation in cars: Connect REM to the car key, 12V directly to the positive terminal of the battery, and GND to the negative terminal of the battery. Alternatively, GND can be connected directly to the car's chassis. This way, the audio system will automatically turn on when the car starts and turn off when the engine is shut down. Installation at home: A 12V-5A transformer is required. "REM 12V to +GND" is a terminal marking specific to car audio systems. REM is primarily used to control the startup and shutdown of the audio system and is generally a wire connected from the audio host.
The REM wire is that thin blue wire behind the audio head unit, specifically responsible for controlling the amplifier's power switch. Last time I installed a subwoofer myself, I connected it—this wire links to the REM port of the amplifier. As soon as you turn on the head unit, it sends an 'on' signal to the amplifier like a remote control. If you don't connect it, the amplifier will foolishly keep draining power, and your car battery could be dead in half an hour. However, some older car head units don’t have a dedicated REM port. In such cases, you can tap into the ACC wire under the steering wheel (remember to add a 5A fuse) and use the ignition key to control the power—just as convenient. When actually wiring it, don’t leave too much exposed wire core; wrapping it tightly with heat shrink tubing can prevent short circuits.
From a decade of experience in car audio, the REM wire is essentially an electronic switch wire. When the head unit is powered on, it outputs a 12V weak current to activate the amplifier, and it automatically cuts off when powered down. I've repaired many cars with battery drain issues after audio modifications, and 80% of them were due to incorrect REM wire connections: some mistakenly connected it to a constant power line, causing the amplifier to keep playing karaoke after locking the car; others connected the REM to the speaker output, resulting in a loud 'pop' at startup that directly blew the speakers. The correct way is to find the blue wire in the main head unit harness and use a multimeter to check the voltage for reliability—don’t blindly trust online claims that 'all blue wires are REM.' By the way, when modifying a high-power system, it’s advisable to add a relay buffer to the REM wire.
Simply put, the REM wire is a trigger line connecting the audio head unit to the amplifier. It delivers 12V voltage when the head unit powers on, synchronizing the amplifier's operation. Last week while helping my neighbor troubleshoot a stereo issue, I discovered his REM wire was pinched and severed by the trunk hydraulic strut. Temporarily patching it with insulating tape caused intermittent connection due to vehicle vibrations. For rewiring, I recommend routing it beneath the driver's side door sill trim to avoid moving parts. Opt for 18-22AWG shielded wiring for maximum durability. If the head unit lacks REM output, you can tap ACC signal from the cigarette lighter fuse as an alternative—just remember to add a diode in series to prevent current backflow.
