I have an 06 f350 with the 6.0 diesel. I have had the stereo installed for about 8 months. Kenwood DNX8120 Head Unit, 1 amp for front speakers, 1 amp for rear speakers, and 1 amp for 10" sub.

A couple days ago, I started getting a buzzing sound though the front and rear speakers with the truck running. When I rev the motor, buzzing changes frequency. When I disconnect the RCA's from the amps, buzzing goes away. I was thinking alternator whine, but why would interference between the power wires and the RCA's start long after installation?

Had a stereo shop tell me to check the alternator and the spark plugs. This was just from my explanation, without looking at the truck. When I told them it was a diesel, they said check the glow plugs...argh. The glow plugs would have no bearing once the engine is warm....right? Makes me think to ignore what they said. But, could a bad alternator cause this? I took the truck to a local repair place that I trust, and they said the alternator was not producing enough voltage to charge the batteries. I have had very intermintent problems with the batteries being week upon cold startup....once every 3-4 months.


Just wondering if I should drop $200+ on an alternator or look elsewhere. Checking other threads, looks like I should check the ground for the amps.

Any opinions? thanks in advance.

Alden

 

If the shop you trust says alternator, try that. My first instinct would have been ground loop in speakers, but it sounds like you have an alternator issue either way. Good luck!

 

Alternator noise should be picked up through the power wires and not so much from inductance in the RCA cables.

First thing I would try is checking for a ground loop, since it will only take putting a DMM on the amp's ground and on the firewall. If you show any significant voltage, then you have an issue to address before moving on. Then I would move the RCA cables, making sure they were 6" away from any other wires (or as far as possible).

Do you have any ground upgrades. Good batteries and lots of grounding will help with this issue. Batteries somewhat filter out alternator ripple, if they start holding less reserve then more ripple comes through.

 

Finally got around to doing some troubleshooting.

Used a multimeter to check voltage between the amp ground, and the firewall, not voltage there. Also checked between amp ground and battery ground. no voltage there.

To rule out the alternator, I disconnected the 10 gauge wire as well as the plug with 2 wires on it. The alternator plug was a bit of a pain...had to wedge a flat screwdriver on the cab-side of the plug to get it to release.

With the alternator completely disconnected, still got buzzing in the speakers. I hooked the alternator back up and tried the stereo one last time....and no buzzing. If it comes back I will let you know.

The only thing I can think is that i did a little off-roading a couple weeks before the buzzing in the speaker started. Some mud got up in the engine compartment. Maybe there was just a bad connection at the alternator plug.

Thanks for the suggestions.

-Alden

 

Mine did this a few weeks before my cheap amp crapped out. Installed a new Alpine PDX amp and all the noise went away. Good amps have better noise mitigation circuitry.

 

Noise came back, ordered a 220 amp alternator from DB Electrical. Will see if this fixes it.

-Alden