How to Turn On Amplifier Without Remote Wire

Norvan Martin
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It can be difficult to install an amplifier in your car if your radio does not have a remote wire (called REM on the amp). The turn-on wire (also known as the remote wire) is a blue line with a white stripe that is situated beneath the head unit. Its primary purpose is to “inform” your amplifier to turn on whenever the head unit is switched on (usually, whenever the vehicle is turned on). To get to this wire, you’ll need to remove the stereo.

In this article, we will explain how you can turn an amplifier on and off if you have a factory stereo with no remote wire. 

The easiest way to turn on the amplifier without a remote wire is to install a high-low adapter with a trigger. In addition, you can run a wire from your ignition switch (or any other 12V wire) to the amplifier. You can also plug the wire into the cigarette lighter, but only if a cigarette lighter turns on and off with the ignition key.

Here is a quick video of the process below:

As previously stated, there are a variety of methods for remotely turning on and off your amplifier, even if your head unit lacks a remote turn-on wire.

Method 1: Use The Fusebox

Getting the turn-on signal from your vehicle’s fuse box is one of the best ways to turn on an amplifier without using the stereo’s remote.

Because the remote turn-on wire is low current, you can connect it to practically any fused output terminal, such as the one for the radio, as long as it only powers up when the car is turned on.

Safety Precautions

Before you begin any work, always unplug the battery. This helps prevent any electrical shocks. Generally, you should take off the negative terminal first.

Tools Required

  • Wire strippers
  • A tool for crimping
  • Either electrical tape or heat shrink tubing
  • A multimeter
  • Different screwdrivers
  • Tools to remove panels (needed for taking out the head unit)


  1. Access the Head Unit: To get to the head unit, you’ll need to use your panel removal tools to take off the dash panel.
  2. Disconnect the Head Unit: Now, pull out your head unit by disconnecting it. Remember to handle the wires and connectors with care.
  3. Find the Fuse Box: Check your car for the fuse box, which you’ll often find under the dashboard or close to where the engine is.
  4. Choose the Right Fuse: You’re looking for a fuse that only gets power when you turn the key in the ignition, like the one for your radio or other accessories.
  5. Test that Fuse: Grab a multimeter and make sure the fuse you picked is only live when the ignition’s on.
  6. Hook Up the Remote Wire: Take a fuse tap adapter and hook up one end of a remote wire to the fuse. Then run the other end to the spot where you’re gonna put your amplifier.

Before connecting the wire to the fuse, use a multimeter to ensure that the fuse from which the signal is coming only receives electricity when the ignition is turned on.

To learn more about how to connect your amplifier remote wire to your fuse box, check out this guide. 

Method 2: Use The Turn-on Module/Trigger

A turn-on module is a little gadget that sends a signal to your amplifier when it is turned on. It can be triggered by any speaker wire or low-level trigger lead.

Here are the steps:

  1. Put in the High/Low Adapter: Hook up your adapter for the high and low signals right to the speaker outputs on your radio.
  2. Hook Up the Trigger Wire: You’ll find a trigger wire on your adapter, and that’s gotta go straight into the remote spot on your amp.

How to Turn On Amplifier Without Remote Wire Trigger

When installed, a turn-on module detects the voltage on the speaker wires of the head unit and sends a +12 volt signal to the remote wire.

Method 3: Use a High/Low Adapter with a Trigger

Another great way to turn on your amp without a remote wire is to use a high/low adapter with a trigger (also known as a line output converter or LOC for short).

Essentially, this adapter detects when the head unit is turned on and provides a remote output that triggers your amplifier to turn on.

Similarly, when you turn off the radio or turn off the ignition, it sees no signal from the speaker-level wires it’s connected to and kills that trigger.

A line output converter is essentially a device that converts the non-pre-amp speaker output (high-level signals) from a factory head unit into a low-level signal suitable for an aftermarket amplifier.

Method 4: Use The Ignition Key

Because stock radios lack a remote turn-on wire, the voltage turn-on signal must come from somewhere, and that somewhere is undoubtedly your vehicle’s electrical system.

Finding a voltage source (part of the vehicle’s electrical system) that only turns on when the ignition is in the accessory or on position, tapping into it, and connecting the turn-on wire to it is the next step. 

How To Wire Remote Turn On For an Amp

It is fairly simple to connect the remote turn-on wire to an aftermarket head unit. Simply connect another blue primary wire to the blue wire in the wiring harness and route the primary wire back to the amplifier, terminating in the remote turn-on terminal.

Here are some suggestions for completing this task correctly and professionally;

Connect to the fuse box

So, first off, identify the fuse box. If you don’t know where it is, consult the owner’s manual for your vehicle. Then glance at your fuse diagram and try to figure out where you want to start.

You’ll need to use a voltmeter and begin probing to check for this. If the voltmeter reads 12 volts when the ignition is turned on, connect the remote turn-on wire to that fuse.

Connect it to the ACC wire

Purchase a quick tap connection, insert the wire to be tapped as well as the new wire, and clamp it down. There is no need for cutting or splicing using this procedure.

Another amazing workaround that uses the ACC wire is to use a relay and the accessory lead that your radio is wired to, which switches it on and off with the key, and your amplifier will now turn on and off automatically.

Connect to any switched 12v power source

Connecting the remote turn-on wire to the Accessory wire isn’t the only technique to make your amplifier turn on and off automatically.

You can utilize practically any 12v switched power supply. If your amplifier is situated in the trunk, for example, you can link its turn-on wire to the fuel pump cable.

Use a power antenna wire.

You can use your head unit’s power antenna as a remote turn-on wire. However, you must ensure that it activates in all modes (Aux, radio, CD, SD card) when the head unit is turned on.

If you connect your amplifier’s remote terminal to the power antenna wire, which only comes alive when the radio is turned on, you will only get output from the amplifier when the radio is turned on.

When you change to a CD, SD card, or another audio source, the amplifier will not function since the head unit shuts off the power antenna cable when the radio portion is not active.

Make use of a turn-on module

A tun-on module is just a little gadget that sends a turn-on signal to the amplifier. Most turn-on modules on the market can generate a remote turn signal from any voltage source that is greater than +0.8V. This implies you can use a speaker cable to turn on your remote.

When the turn-on module detects a voltage on the speaker wire, it sends a +12 volt signal over the remote wire to the amp’s turn-on circuit.

Symptoms of A Bad Remote Wire

Bypass your car’s present remote cable. This will notify you if there is a problem with the amp or the wiring. If it does not power the amp, it is faulty.

How to Wire Remote Turn On For An Amp

If the remote wire on your head unit isn’t working for whatever reason, or if you’re using a factory stereo, you can connect it to the fuse box. The radio is often the best fuse site to tap into.

Here are some simple methods for connecting your amplifier to a fuse box;

  • Take the radio fuse out of the box. You may need to consult the user manual to find it. 
  • Wrap the remote wire around one of the fuse’s metal pins at the top.
  • Insert the fuse back into the holder.



To wrap things up, getting an amplifier to work in your car when there’s no remote wire from the stereo might seem tough, but there are a few good ways to get around it. You could use a high-low converter that comes with a trigger, connect to a 12V power source like the ignition or car lighter, or go for a turn-on module.

These strategies all do the trick for turning on your amp remotely, so cars with original stereos can still get a sound upgrade. Just make sure you stick to the setup instructions properly; and if you want the best outcome, maybe think about asking for expert help.

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Norvan Martin is the founder of He is a professional Electronics Engineer and is passionate about home theater systems and AV electronics. BoomSpeaker was created as an online hub to share his knowledge and experiences as it relates to home theaters and home audio electronics. My email: [email protected]  Connect on Pinterest and Linkedin