How to Fix Common Car Amp Problems

A quick troubleshooting guide

This article explains six common car amp problems and how to fix them.

The common car amp problems that one might experience.
Lifewire / Miguel Co
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If the Amp Doesn't Power On at All

To turn on, the amp needs power at both the remote and power wires, in addition to a good ground.

If the remote turn-on wire doesn't have power, your amp won't turn on. The remote wire acts like your finger flicking a switch, where your finger is battery power, and the switch is a mechanism inside the amplifier.

The remote turn-on wire usually comes from the radio, in which case the amplifier won't turn on if the radio isn't on. So if there is no power at the remote terminal on the amplifier, the next step is to check for power at the corresponding wire where it connects to the radio.

If the amp is wired incorrectly, and the remote turn-on is connected instead to the power antenna wire on the head unit, the amp might power on only sometimes. In this situation, the amp typically will turn on only when the head unit audio input is set to AM or FM radio.

The power wire is the next thing to check if you find no problems with the remote wire. This wire is thicker than the remote wire, and it should have battery voltage. If it doesn't, check for any inline fuses and verify that the wire isn't loose, corroded, or shorted out somewhere.

If the remote and power wires both check out OK, the next thing to look for is continuity on the ground wire. If the ground connection is poor or isn't connected at all, the amp might fail to turn on or not work very well.

If the amp has good power and ground, the remote wire has voltage when the head unit is turned on, and no fuses are blown, then you're probably dealing with a busted amplifier.

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If the Protect Mode Light Turns On

Some amplifiers go into amplifier protect mode to avoid further damage to internal components. If your amp's "protect" light is on, chances are you have a faulty speaker, subwoofer, cable, or another component. Check for power, as outlined above. Then, look at individual components.

First, unplug the speaker wires. If the light turns off, the problem probably lies in one of the speakers. To determine ​where the problem is, visually inspect each speaker and subwoofer in your system.

A blown speaker could be the cause of the problem. You can also use an ohmmeter to verify that none of the speakers are grounded out, which can occur if speaker wires become loose and contact the ground, or if the speaker connections are in contact with bare metal.

If you can't find any problems with your speakers, check the RCA patch cables. To check this, hook up a set of good RCA cables to the head unit and amp. If that causes the light to turn off, replace the RCA cables.

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An underpowered amp or inefficient speakers are typically the cause of clipping in a home audio setup. Loose or burnt wires can introduce similar problems in cars.

An underpowered amp is the single most likely cause of clipping, in which case you'll need to either upgrade the amp or downgrade the speakers. Compare the amp's power rating with the speaker.

If the amp has plenty of power for the application, the problem might be in the speaker wires, the speakers, or the amplifier's ground.

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If No Sound Is Coming From Your Speakers

If the amp turns on, make sure that it receives an input from the head unit. This is an easy process if you have access to both the head unit and the amp. Simply unplug the RCA cables from each unit and reconnect them with a good set.

After verifying that the head unit is turned on and the volume is turned up, cycle through the inputs (such as the tuner, CD player, or auxiliary). If everything works after bypassing the installed RCA cables, replace them with a good set. If you get sound from one input but not another, the problem is in the head unit and not the amp.

If you still don't get any output from the amplifier, disconnect it from the speakers in your vehicle and hook it up to a known good speaker that isn't in your car. If the amp drives that, the problem is with the speakers or wiring. If you still don't get any sound, the amplifier might be faulty. Check that it isn't in "subordinate" mode and that there aren't any conflicting filters before condemning the unit.

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If You Hear Hissing or Other Distortion

Inspect the patch cables and speaker wires. If the cables that connect the head unit and amplifier run alongside any power or ground cables at any point, they can pick up interference that you'll hear as distortion.

The same is true of the speaker wires. The fix is simple: Reroute the wires so that they don't come close to any power or ground cables, and that they cross at a 90-degree angle if absolutely necessary. Using higher-quality cables or wires with good shielding can also help.

If you can't find any problems with the way the patch cables or speaker wires are routed, unplug the speakers from the amp. If you still hear noises, check for a bad ground.

The problem might also be in the head unit or whatever else you use as an audio source. For more information on how to diagnose that type of problem, learn how to deal with ground loops in car audio systems and identify and fix other issues with your car stereo speaker.

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Strange sounds can come from a subwoofer that's overpowered, underpowered, or installed incorrectly, so getting to the bottom of this problem can take some work.

First, eliminate problems with the speaker enclosure. If the enclosure isn't the right fit for the sub, the sub typically won't sound right. An improperly mounted speaker can allow air to escape while you're listening to music, as the vibrating speaker cone drives air into and out of the box past the seal. Seating the speaker properly to stop the resulting fart-like sounds.

If there's nothing wrong with the enclosure, make sure that the woofer is impedance-matched. Impedance matching is simple if you have one sub hooked to one amp; it either matches or it doesn't. If you have multiple subs hooked to a single amp, you'll need to do some calculations based on whether they're hooked up in series or parallel.

If the impedances match, check the power ratings of both the sub and amp, and make the necessary corrections if the amp is under-powered or over-powered. If you're simply overpowering the sub, get a bigger subwoofer or don't overpower it (for example, turn down the gain at the head unit, turn down the bass boost, and adjust all the settings until the woofer stops farting).

  • How do I diagnose a blown amp fuse?

    To diagnose a blown car amp fuse, replace the fuse with everything turned off. If the fuse blows, there's probably a short between that fuse and the rest of the system. Next, replace the fuse again with the amplifier disconnected. If the fuse still blows, there is a short somewhere in the wiring. If the fuse blows when the amplifier turns on, there is probably an internal problem with the amplifier.

  • Why does my stereo amp turn on and off by itself?

    If your car amp turns on and off by itself, it could be due to overheating or amplifier wiring problems. The car amp could also be in Protect Mode.

  • How do I fix a broken RCA jack on an amp?

    To fix a damaged amp jack, disassemble the amp and use a soldering iron to remount the connector onto the PCB board.

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