longbedbob

Base 4.3" radio.
New Infinity Reference 704A amp behind rear seat.
2 x PAC SNI-35 Line out converters, grounded.

Problem: With the radio off, I have some base level static that sounds like a faint radio station. Seriously. With the engine running, I also have some mild alternator whine. Noise slightly worse on rear channels. Road noise masks the whine when driving, so it's really only discernible at idle. Regardless, neither gets louder as the volume increases. As I said, it's just a "base level" static that doesn't get worse but it always there.

Intitially: Infinity speakers connected to radio using stock harness. No problems.

Amp install: Noise with crappy Infinity LOC connectors that came with the amp.

- Ordered and installed PAC variable line out converters and installed (using grounds with the LOCs). Noise better but still there. Relocated ground with no effect.

- Undid all wiring (save inside doors), spliced directly into harness behind the head unit and soldered/heat shrink on all connections. Despite removing all sorts of dangling wires and crappy crimps from the equation, it's still there.

- After all that, I ran a 6 gauge ground wire through the rear cab vent and tapped it to the frame. No difference.

-Power wires run on driver side and shielded RCA cables ran on PAX side.

- Swapping RCA cables from front to rear doesn't change anything. The noise is still slightly worse on the rear channels regardless of the source of the input. The noise does go away when the RCA cables are removed completely. That should exclude the amp as the problem.

At this point there's only a few things left to try:

1. Remove the LOCs, solder in speaker wire from the front of the cab to the rear seats and then reinstall the LOCs closer to the amp. Maybe a higher level signal will be less susceptible to interference, but I doubt it.

2. Dial down the input signal level at the LOCs, which are currently set at 1/2. I previously tried this with no effect, but that was before soldering everything. Possibly try this in conjunction with lowering the amp's gain, also currently about 50%.


3. Tear apart the doors and solder the original installer's crimps and look for bare wires. I doubt this will work, either, because the sound goes away when I remove RCA cables indicating the problem is before the amp.

4. Lastly, just accept that I have a noisy head unit or one that might have internal radio circuitry and that could still be working despite being powered off. No matter what I try downstream, the problem will always be there.

JKoop

I'd connect to the PAC at the back of your truck, near the amps. Yes, high level signals will have less chance for interference issues.

I am wondering if the noise is with the PAC itself. Once you run the signals back to the PAC in back, it's easy to just go right to your amps and bypass them as a test. If you get rid of the PAC and the noise is gone you have an easy solution: Use ForScan to eliminate the Ford EQ and it will also switch to low level signals. That's what I'm doing. I have the ForScan device, got it yesterday. I'm going to solder RCAs onto the speaker wires coming from the head unit, into a JL Audio TWK DSP, then on to my amps.

longbedbob

Good tips, thanks.

I'm going to just install the PAC dash kit and a new receiver, running quality RCAs. If that doesn't do it, then I might revisit running speaker level signals and downconverting at the amp.

One more possibility would be to ground the new head unit in a new location. But I hope it doesn't come to cutting up and running yet more wire.

crankinaway

Nope. I have tried everything to rid myself of the same floor noise. There was a lengthy thread a while ago. I have come to the conclusion that its something in the factory radio that causes it.

I regrounded, used high levels, low levels, swapped RCAs, swapped speakers. The best I can do is keep the gain relatively low and then I can't hear it over my exhaust.

I should note that I have not tried using forscan to eliminate the ford eq.

JKoop

Well damn. I am going to tear into my '17 this weekend. I HOPE I won't end up with annoying noise issues!

Where did you run your ground? I see a lot of grounds are on the back wall in the rear. My stereo guy says they ONLY ground fords at the frame - run the ground through the floor in the back and go right to the truck frame. maybe there is something to that.

longbedbob

I've tried the factory ground at the rear of the cab, the rear seat mount, made my own ground to the floor and eventually ran 6 gauge wire from the amp directly to the frame via the cab vent. Yes, I ground off the pain each time.

Something that one could try is to reground the head unit. One of the techs at Crutchfield recommended running it to the same location on the frame where the amp is grounded.

I've thrown in the towel and am upgrading to a Kenwood deck. That will eliminate all of the factory bits. If it still persists after all that, I'll reground the radio and install new, thicker power wire.

crankinaway

I will add to what I already listed.

I regrounded the factory deck, tried running a ground from amp directly to the battery and also ran RCAs, power and ground outside of truck to eliminate interference from other devices. Nothing.

I have recently ordered a MX device to try the eq forscan mod.

I do not get any whine only floor noise. Its a bummer that I have to keep the gain unusually low because it is hurting the performance of the system.

I will note I am running base 4.3 deck, JL amp, sub and door speakers.

When I discovered the static I actually reconnected the factory harness unamped and if you put you ear to the speakers....it makes the noise bone stock albeit it is really difficult to hear.

longbedbob

Update:

New Kenwood head unit and the PAC dash kit has helped a bit.

I've gotten rid of one out of three noises that I had.

1. The alternator whine is still there.
2. Static is still audible when the truck isn't running.

The radio station in the background is gone, however.

More in a later post.

longbedbob

Update 2:

After re-re-re and relocating grounds the problem was still there.

Eventually I ran the grounds outside the firewall and the rear of the cab and bolted directly to the frame (after grinding off the paint).

No joy.

I then disconnected the 12v constant from the head unit and wired it directly to the battery. I followed with the 12v switch power and used a relay to provide clean juice from the battery.

The static disappeared but the alternator whine was still present.

On a hunch, I moved the grounds back into the cab and wired up the head unit ground to the factory harness.

Whine gone.

So, it appears that I had a "dirty" power issue. Getting it directly from the battery seems to have fixed my problem.

I can't tell you why and, barring an electrical problem somewhere else, will probably never know.

I called the dealership and they don't want any part of it now that I've been into the dash and installed a radio. They are content to say that I caused it despite the problem seeming to be "upstream" of the head unit.

crankinaway

I agree with dirty power which is back feeding into the speaker signals. I thought about your relay idea but I couldn't bring myself to tear the dash apart again.

Is your deck holding presets/time using this method?

I just got my MX link so I am gonna give the ole Forscan eq mod a try and also low level inputs.