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[SOLVED] Car Amp Turns On, But No Sound From Subwoofer

Car Amp Turns On But No Sound From Subwoofer

You’re on a road trip with your family, enjoying your favorite beats. And suddenly, the sound stops coming out of the subwoofers.

It’s equally frustrating and puzzling as all your audio components are seemingly fine (the car radio is turned on, the green LED is blinking on the amplifier, etc.).

Based on my observations, it’s due to some fault in RCA outputs, speaker inputs, the amp’s power/ground connections, the amplifier, or the subwoofer itself.

We’ll have to check for each of them to find out the root cause of this issue. You can also apply these tips if no sound comes from your car speakers instead of the subwoofer.

9 Reasons Why Car Amp Turns On But No Sound From Subwoofer

#1. Car Amplifier In Protect Mode

Amp Protect Mode

One of the most common reasons you’re not getting any sound out of the subwoofer is the protect mode in the amplifier.

It’s a safety mechanism that prevents the amps from permanent damage due to electrical overflow. It either shuts them down or reduces their output.

To check if this mode has been activated, you’ll have to look for a red-colored LED light with the ‘protect’ label against it. If this LED is turned on, your amp is in protect mode. And you have to get the amp out of this mode to solve your issue.

We’ve already discussed how to do it in another post, so I won’t fully explain it here. But to give you a rough idea, you need to make sure the subwoofer and amp are compatible (in terms of impedance), check head unit wiring, check the battery voltage, check fuses, etc.

#2. Damaged RCA Cables

RCA Cables

If your amplifier is not in the protect mode, we’ll check the RCA cables. These wires send the preamp output signal from the head unit to the amplifier.

The first thing we’ll check is the wires themselves. Make sure they’re not damaged, frayed, or have loose connections. Sometimes a wire looks fine from the outside but is damaged from the inside. To rule out this possibility, you can temporarily replace the RCA cable with a new one to see if anything changes.

The second thing you need to ensure is that these cables are plugged into the RCA inputs of your amplifier, not the RCA outputs.

Although straightforward, many confuse these two by plugging these cables into RCA outputs, resulting in no sound output.

Similarly, I’ve seen many new car audio installers plugging the second end of RCA connectors into the RCA video outputs of the radio (usually colored yellow) instead of the preamp RCA outputs (usually colored red and white). Make sure that you’re not making this mistake.

#3. Mismatched Speaker-Level Outputs

Speaker-Level Outputs

If you have a factory head unit with speaker-level outputs, please confirm that you’ve correctly matched the wires with the wiring harness on your LOC or amp with the high-level inputs. You can go through the owner’s manual of your LOC or Amp for more information in this regard.

#4. Mismatched Speaker Wires

These are the wires that connect your amp to the speakers or subwoofer. You need to check that these wires are correctly connected to their supposed terminals.

Some people make this mistake by connecting these wires regularly in bridged mode. In reality, you have to connect the positive wire to the positive terminal on channel one and the negative wire to the negative terminal on channel 2 in that mode.

Similarly, you need to ensure that the other ends of this wire are tightly connected to the speaker terminals of the speakers/sub.

Lastly, you’ll have to check that the positive and negative speaker wires match the polarity when connected to their terminals. The subwoofer will not produce any sound output otherwise. Simply put, the negative wire should be connected to the negative terminal, and the positive wire should be connected to the positive terminal.

#5. Loose Amplifier Cables

Amp Cables

Apart from the speaker and RCA cables, additional wires are connected to the amplifier’s power, remote, and ground terminals.

The first one is the power cable which connects the power terminal of a car amplifier to the positive terminal of the car’s battery.

The second is the remote turn-on cable that turns the amp on/off with a 12V signal.

The last one is the ground cable which connects the ground terminal of the amplifier to a bare metal point on the car’s chassis (for grounding).

You’ll have to make sure that these wires are of the correct gauges (too thin cables will not allow the current to flow correctly) and are not pinched or damaged.

You can also use a multimeter to test the voltage at power and remote turn-on wires.

#6. Malfunctioning Subwoofer

The subwoofer or speakers often don’t produce sound simply because they’re faulty.

They can have a short circuit, have their cone or voice coil(s) burned, or be wired out of phase – all of these things can lead to no sound output.

Therefore, you should plug a spare subwoofer (that’s 100% functioning properly) into your audio system to see if anything changes.

#7. Incorrect Input Gain

Input Gain

Another thing you can check is the input gain on your amplifier or the bass knob (if your amp has one). If the gain is set to level 0, you won’t be able to get any sound. Similarly, you’ll get sound distortion if it’s set to max level.

In essence, you should set it somewhere in between these two extremes.

#8. Incorrect Head Unit Settings

Head Unit Settings

Sometimes, the speakers or subwoofer stop producing sound output not because of any hardware issue but simply due to head unit settings.

Many head units come with an ‘RCA disable’ option under the fader/balance area, which (if turned on) can disable the RCA preamp output.

Similarly, some other head units have a ‘subwoofer output’ option in the sound settings. This option must be enabled to get a sound output from the subwoofer.

The other settings you should check are the crossover (Low-Pass filter and High-Pass filter) and gain level output.

Related article:

#9. Weak Car Battery

If all components of your vehicle’s audio system work fine, but the subwoofer still has no sound output, it’s time to check the battery.

The voltage drops if the battery malfunctions or is not fully charged. And that drop will cause the car audio system not to work as expected.

Therefore, check the battery with a multimeter to confirm whether it’s giving a 12V+ voltage.


So these are some common reasons you don’t get any sound output from the car subwoofer even when the radio is turned on.

Although testing for all components might seem lengthy and tedious, it’s necessary to do so as there’s no definitive way to fix this issue.

If you’ve followed the abovementioned steps and the issue still exists, I suggest hiring a professional mechanic. That’s because the problem seems too deep-rooted for DIY.

Frequently Asked Questions

How To Fix The Car Amplifier Low Volume Problem?

Check the amplifier gain settings if you’re having low-volume issues with your car amplifier. If that’s good, check the head unit’s EQ/volume settings, RCA cables, and audio source, as these are the usual culprits for this problem.

How To Fix No Power In Car Amplifiers?

If your car amplifier is not getting any power, you should check the fuses (both internal and in-line fuses). If those fuses are not blown, check power/ground wire connections, remote turn-on wire, battery voltage, etc.

Why Is My Car Amp On But No Bass?

If your car amplifier is powering on and you’re not getting any bass, check the head unit settings (make sure the high-pass filter is turned on and the phase setting is correct). After that, check the subwoofer wiring/ enclosure and amplifier gain.

What Are The Symptoms Of A Ground Loop In Car Audio?

Common symptoms of a ground loop in a car’s audio system include humming or buzzing noise, alternator whine (varies according to the engine RPMs), increased distortion and muddiness in the sound, and the amplifier shutting down.

Can Bad Ground Cause No Sound?

A bad ground can prevent the proper current flow (reduced power supply to the amp), increase electrical noise/interference, or send the amp into the protect mode. These issues, in turn, can result in no sound output.

What Causes Car Subwoofers To Fail?

Common reasons behind car subwoofers’ failure include subwoofer overpowering, poorly designed enclosure, improper installation, external damage, moisture/warm temperature exposure, and manufacturing defect.


John is an automotive enthusiast who has been passionate about cars and car audio systems for over 25 years.

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