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How to Eliminate Engine Noise

Engine/Alternator noise sounds like a high pitch whining that gets louder and higher in pitch as you press on the gas pedal. This noise indicates that the system either has a bad ground, defective head unit, defective amplifier, bad RCA cables, improper installation, or a problem in the vehicle’s charging system. Follow the steps below in order to pinpoint the cause of engine noise and reduce or eliminate the problem.

Unplug the head unit’s power harness before connecting or disconnecting the RCA cables and then plug the power harness in. It may seem redundant but it may prevent further problems.

Test while the engine is running; alternator noise is only produced while the engine is on.

1) On the head unit, turn the volume down to zero.

2) Turn the gain up on the amplifier until you can hear the engine/alternator noise.

3) Unplug all of the RCA cables at the amplifier.

  • If the noise is no longer audible, then the noise is being produced before the amplifier. This means the noise is either coming from the RCA cables or the head unit. (go to step 4)
  • If the noise is still audible, then the problem stems from the amplifier or power wires (go to step 8)

4) Plug the RCA cables back into the amplifier.

5) Unplug the RCA cables from the head unit.

  • If the noise is still audible, then the noise is being produced by the RCA cables (go to step 6)
  • If the noise is no longer audible, then the noise is being produced at the head unit. (go to step 7)

6) First, remove the RCA cables from the vehicle. Plug them into the head unit, run them over the carpet and chairs, and plug them into the amplifier.

  • If the noise is gone then you have successfully isolated the problem.  In this case, having the RCA cables next to the amplifier’s power wire or on the body of the vehicle is the cause of the engine noise.  Electrical noises in the wire(s) are picked up by the RCA cables and amplified by the aftermarket amplifier.  To prevent this from occurring, run them on the opposite side of the vehicle from the power wire and avoid running them near any antennas or antenna cables.  You should also try to keep the wires off the body of the vehicle as much as possible; run them between the carpet and the padding.
  • If the noise is still present then you may want to try repeating step 6 with a new set of RCA cables.  If the noise is no longer audible, then your RCA cables need to be replaced.

Higher quality RCA cables with more shielding will help reduce these types of interferences and will improve your system’s sound quality.  Ask a Sonic Electronix representative for recommendations.  I personally suggest NVX.

7) Find a clean metal surface (without paint, grease, or any other coating on the metal), preferably on the chassis, for a new ground. Ground the black wire from the head unit’s harness to the metal surface. For a better ground, also connect a wire or back strap from the chassis (back) of head unit with the bolts provided by the manufacturer and connect it to the same grounding point that you used for the grounding wire.

  • If the noise goes away, then you have successfully isolated the problem.  The head unit just needed a better ground.

GROUND LOOP ISOLATOR: they are inexpensive and easy to install but they do not always help. Also, it may cause a small loss in your system’s sound quality.  Follow the steps below to find out if it will help:

1. Unplug all of the RCA cables except for one of the channels that is producing the noise.

2. At the head unit, wrap one end of a copper wire around the outside ring of the connected RCA cable. Use electrical tape to keep it secure and connect the other end to the amplifier’s ground.  If the noise goes away, then adding an isolator will likely help eliminate the engine noise.  If the noise does not go away, then it may not be worth buying an isolator. Follow the installation instructions provided in the isolator’s packaging and install it at the head unit.

INLINE POWER FILTER: will only work if the power wires are delivering “dirty power” to the head unit.  The only way to find out it will work for you is to buy it and try it. Follow the installation instructions provided in the packaging.

***It is possible that the head unit may be defective and have an internal grounding issue.  It is a common issue in Pioneer head units since they have an internal ground fuse to protect them.  If the RCA cables are plugged in after the head unit’s power harness is connected, the internal fuse may blow.  If the fuse is blown, the unit will have to be sent to an authorized repair facility to be replaced.  To avoid this, connect all of the RCA cables before plugging in the head unit’s power harness.

8) With the RCA cables unplugged, find a clean metal surface (without paint, grease, or any other coating on the metal) and reconnect the ground.  For the best possible ground, go through the vehicle’s body and connect the ground wire directly to the chassis underneath the vehicle.  Connect all amplifier grounds at the same point on the chassis. The best ground is the shortest ground, and the ground wire should be the same gauge as the power wire.  A larger gauge is always better.

  • If the noise goes away then you have successfully isolated the problem.  Talk to a Sonic Electronix representative for recommendations on the best amplifier kit or power wires for your application.  I personally recommend NVX or Kicker power cablesbecause they have true wire gauge sizes.  Most off-brand kits do not have true wire gauge sizes.
  • If the noise does not go away either the amplifier may be defective and need to be tested, or your vehicle’s charging system may need to be checked.  Contact the Sonic Electronix warranty department to have the amplifier tested and exchanged/repaired if necessary.  Contact your mechanic to have the charging system checked.  It is possible that the vehicle’s AC/DC converter is not properly working and there is a small AC signal present in the power wires.
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Staff writers at Sonic Electronix are experts in their field. In addition to a complete in-house training program, these experts typically have many years of hands-on experience in their specialty. Some come from car audio installer backgrounds, while others come with extensive retail experience.
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