Grounding and noise

Hello,

Car: Lexus LX470, 1999

On the wiring diagram, there is one connection that I can't figure out, it's called AGND. Wire is BROWN / White and a small arrow pointing at the connection, saying 2000.

(Regular GND exist too, and, according to diagram, it's grownded under front passenger's seat)

Any ideas what this is, would be appreciated,

Thank you in advance

Thank you!

Now, the next question then, which one do we use for aftermarket head unit? My assumption is it's GND that we need. And if so, what do we do with AGND? Just leaving it not connected?

Thanks!

Gentlemen,

As someone kindly explained to me that AGND on the wiring diagram most likely means 'Analog Ground' my question then would be. What is 'Analog Ground'?

Provided that on the OEM head unit there's also a regular Ground, which is ends up by being connected to the chassis, I am concerned about which one do I use with the aftermarket head unit, with just one ground connector?

Hope someone can shed a light on this!

Many thanks in advance

Thank you Haemphyst!

No, there is no DGND connection. It's Lexus LX470 and AGND is a connection between HU and factory amplifier.

Thanks!

Thank you sir, I'll give it a try.

Gentlemen,

Looks like I am having another grounding problem.

Here's the system set up:

Lexus LX470. Head Unit - Sony WX-S2200

I have replaced the head unit, but kept factory amplifier and speakers. (for now at least)

Amplifier is located under passenger seat, and grounded to a chassis too.

Ground wire goes from the amplifier to the head unit harness.

So here's my problems with and without engine running.

1. Ground wire from amp harness connected to ground of a HU - loud popping sound when switching between tracks of a CD, regardless of engine running or not. No other, engine, noises are present then.

2. Head unit ground wire connected to a chassis - less popping sound when switching tracks, but noise when engine is running.. Noise is independent of RPMs, stays constant, not varies in volume and reminds me of ignition rather than alternator. Not very loud too, only audible when volume is almost all the way down.

3. HU body connected to a chassis through mounts, HU Ground hooked up to a chassis. NO popping sound when switching tracks. Engine noise the same as at #2.

When HU grounded to a chassis, resistance between negative terminal of a battery and HU ground wire is about 0.9 Ohms.

I even tried running a wire directly from battery negative to the HU ground, without any luck.

Honestly, I am out of ideas at this point. Have tried pretty much everything, DC noise filter, grounding either HU or Amp harness to a chassis, (or both) - no luck.

Any help or advise will be very much appreciated,

Thank you

What gauge wire are you using from the HU to the chassis ? Also, have you tried changing HU's ? There maybe something wrong with the HU's ground or power filter's. Just some suggestions for you.

Thank you guys!

In fact, I'm not sure about what gauge the ground wire is. It is about 1.5-2mm in diameter. Go figure. Same diameter as the ground wire of the OEM harness.

Unfortunately switching HU is not as easy, I don't have access to them, and purchased this one on the Internet from Japan.

However, the fact that it makes noise when it touches the metal of the car, and popping when it is not, makes me think that it may not be a headunit issue. Otherwise it would be doing something constantly, no?

Forbidden: Thanks for the suggestion, I'll try and hook up a speaker directly to the speaker output of the headunit. See what happens. And again, when it is not in the cavity, it pops when switching between songs, but no noise when engine running. If it is in the cavity, but not bolted to the mounts, same thing, when bolts are in place, there's this noise, but no popping. Go figure.

And in order to connect it to the existing car harness, I had to actually make my own connector, matching the one on the OEM radio. Used plasticine, epoxy and contacts, then soldered it to the Sony harness.

Thanks again.

Thanks Geepherder, but no, I am not feeding factory amplifier with speaker output signal.

Sony does have two sets of preamp outputs, and that's what I'm feeding the amp with, through the factory harness.

Besides, I believe that if the signal was too strong, it would be the case regardless of the engine state.

But you're right, above mentioned problems were not present with the factory head unit.

Thanks again for your input!

Just as a follow up.

Connected HU to the chassis (seat mount bolt) with 10 gauge cable, no difference, noise is there, just as when HU touches the metal of the car.

Tried hooking up speaker directly to one of the speaker output of the head unit. Noise is NOT there.

Last thought is to re-run the amplifier ground closer to HU? Does that make any sense at all? Amplifier works with no noise with the OEM radio.

So challenging!

Thanks in advance

Thanks Forbidden,

I'm not sure what do you mean by monster hot signal.

I kind of thought that line output is pretty much the same everywhere. And, as I mentioned earlier, speaker outputs of the head unit are normally left not connected.

What I'm feeding amplifier with, is the preamp output from SONY, which has four RCA at the back, front and rear. And otherwise sound is very clear and good, which wouldn't be the case if the signal was way out of amplifier range.. Or am i wrong?

Thank you again!

Not necessarily.  The factory deck may put out a lower level signal than the new deck.  Some line out converters are adjustable which could give your amp a usable signal.

You can also try linking your headunit ground to the amp ground.