Once you purchase one of our best car amplifier picks and you learn how to install the amp, you expect clear, crisp sound. Sometimes, amps simply wear down over time, leading to an unpleasant sound experience, but other times, there is a problem you can fix. Thankfully, it doesn’t take a lot of effort or knowledge to diagnose a faulty amp. We’ve put together some of the most common problems in this car amplifier troubleshooting guide to help you find the issue.
By taking the time to find the trouble on your own, you save money and take pride in fixing your car stereo system.

Amp Doesn’t Power On

  1. Check the voltage on power wires (should be around 12 volts when the car is off and 14.4 when on).
  2. Check the voltage on remote turn-on wire (should be at least 5 volts).
  3. Measure ground wire continuity.

If everything is correct, you must check the in-line fuse and amp fuses. You can read each side with a voltmeter, and it should measure 12 volts. If any of them are blown, you must replace the culprit.
If all of the above looks normal, your amp is defective and requires replacement.

Protect Light Comes On

  1. Start by troubleshooting as you did for no power.
  2. Unplug the speaker wires. If the protect light turns off, check the sub and speakers for defects. It’s possible that one of the wires came loose and started touching metal, which causes the speaker to short.
  3. You also want to check the source unit and RCA cables. If the RCA cables are grounded, burnt, or pinched, you will experience trouble. Grab extra RCA cables and plug them in from the amp to the source. If the light goes off, you need to replace your cables.

Amp Has No Output

  1. Make sure the amp is turning on, with the above steps.
  2. Connect a new set of RCAs. Connect them from the source to the amp. If this creates output, your RCA cables are bad.
  3. Attach an external speaker to the system. If that speaker produces sound, you have an issue with your speakers.
  4. Check the amp’s crossovers and settings. You need to ensure that the subsonic filter and low-pass filter don’t conflict.
  5. If your amp has a master and slave setting, make sure you have it set as a master, unless it’s connected to another amp.

Clipping Amp

  1. You must check the power of the amp to ensure it’s enough for the subwoofer. If it’s not producing enough power, it causes a clipping sound.
  2. Unplug the speaker wires and continue playing sound. The power, ground and RCA cables should still be connected. If it stops clipping, one of the speakers is shorting out or your wire is burnt.
  3. If the amp continues after disconnecting the speaker wire, you must check the ground connection. It might have come loose when you went over a bump.

Subwoofer Slaps or Pops

  1. Ensure your box has the right specifications for the subwoofer.
  2. Check the subwoofer wiring to the impedance to ensure it is correct.
  3. If the mount surround isn’t airtight, you will experience an air leak from the box, which creates sound.
  4. Examine the power ratings of the sub and amp.
  5. If the amp is providing too much power, you need to reconfigure it. Turn down the gain from your head unit and ensure all of the equalizers are zeroed. Then, adjust the bass boost down and check your other settings.
  6. If the subwoofer isn’t getting enough power, you will experience distortion. Consider adding a line driver to provide more voltage.

Crackling, Hissing, Background Noise or Distortion

  1. If the speaker wire or RCA cables are run near the ground cables and power cable, you will get feedback.
  2. Unplug the speaker wire and test. You shouldn’t hear anything through the speakers at all. If you do still hear the distortion, you want to check the ground wire and ensure continuity.
  3. Check the source. It can pick up distortion and send it to your amp, where it becomes worse.

If none of these resolve the situation, the car amplifier troubleshooting guide led you to a defective amp.

Hearing Engine Whine

Typically, this is because of the ground. You don’t want to ground an aftermarket unit to the factory ground, because your unit is more sensitive than a stock version.

  1. Check the amp ground. You should ground it to the negative terminal of your battery, but that’s not possible when it’s in your trunk. The shorter the ground wire, the better. If you can’t get to the battery, use a clean chassis ground. Just make sure that no paint is present.
  2. Don’t run the RCAs along with the power or ground wire.

Overheating Car Radio

  1. Check to see if the wires are blocking the head unit’s fan.
  2. Are wires shorting out the ground? It’s also possible that two wires are in contact with one other.
  3. Check the impedance of the speakers. You want to ensure the head unit is stable.
  4. Check the ground with your voltmeter. Ensure it has a clean connection and makes contact.

If none of these are the culprit, it’s likely that your car amplifier troubleshooting revealed that the head unit is defective.

Overheating Amplifier

  1. Check the airflow to the amp.
  2. Examine the wiring. Ensure that the subwoofers and speakers are wired together with an impedance that the amp remains stable with.
  3. Check the amp voltage while playing. If it goes below 12 volts, you don’t have enough power, which forces the amp to work harder.
  4. Check the ground with your voltmeter. Ensure it has a clean connection and makes contact.

If none of these are the culprit, it’s likely that the amp is defective.

Car Amplifier Troubleshooting Made Easy

This basic car amplifier troubleshooting guide is only the basics. There are hundreds of reasons you might experience trouble with your car stereo system. If none of these solutions helped you, we recommend that you read the owner’s manual.
You will also need to walk through your install again to make sure you set everything up correctly. If you are able to troubleshoot a defective amp on your own, you save yourself plenty of time waiting for professional repairs.
Don't see your issue on this list? Check out our Common Car Stereo Problems, Symptoms and Solutions article to see if we can answer your car's issue!