Thoughts on eliminating ground loop in ipod2car

dan326 · Post by **dan326** » Fri May 13, 2005 1:51 pm

I have installed my ipod2car and am getting some alternator whine. First I will describe the install.I have the gm3 harness. It has no ground wire. I have connected the power wire for the adapter to the power wire of the HU. The HU wire is blue/ wht stripe. I have the power wire of both HU and adapter wound and in one end of a wire splicer. The HU wire connects in the opposite end.The noise I experience is as I accelerate, the pitch gets higher. When I shift, the pitch drops and starts over again. The noise is noticeable when I have the volume of my HU up and there is either a quiet spot in the music or if I have my ipod paused.Peripheral has a ground loop isolator that can be modified to work with the adapter. A couple of questions.Will this help?Will the sound quality get worse?How does this GLI work?Does my install sound different from anyone else's?All input is appreciated.

Jahntassa · Post by **Jahntassa** » Fri May 13, 2005 11:27 pm

I've always had noise issues in the Vibe. Even with the Nav system.GLI's can help. Basically, it's a small transformer. It just keeps the iPod from electrically connecting to the radio.. Now.. If they have a specially modified one, i'd say go with that..1. It could help, but it could not.. Usually it'll help some, if not more.2. No, not really. You might notice a slight drop in volume, but it should be too bad.3. As said, it's basically a small set of transformers that electrically isolate the ipod box from the radio.4. As said..no..it's a chronic (and annoying) problem..

dan326 · Post by **dan326** » Fri May 13, 2005 11:51 pm

Peripheral has a GLI that can be modified for this particular adapter. I can't figure out why I would be getting the noise and no one else who has one is getting it. I thought maybe I did something wrong on the install, but I don't see what my other options were. Where does the GLI usually go?Would going straight to the battery help?Will a power line filter help?

GMJAP · Post by **GMJAP** » Sat May 14, 2005 6:00 am

Let me ask you this before you get the filter - Is your iPod running off power from the car? If so, the noise could be coming from the iPod - getting in through the DC adapter. (Or does the ipod2car power it? Either way, it might be a power supply noise problem.)

dan326 · Post by **dan326** » Sat May 14, 2005 11:06 am

The adapter makes this noise even if the pod isn't hooked up.I can just change to the pod source and turn the volume up on the hu and I get the whine.

Jahntassa · Post by **Jahntassa** » Sat May 14, 2005 12:31 pm

A power filter would be a good way to go, but there's no guarantees what will help...1) In-line with the audio to the radio.2) Maybe, but usually that's what would create it, having two different power sources. You can try it, though.

GMJAP · Post by **GMJAP** » Sat May 14, 2005 1:24 pm

Quote, originally posted by dan326 Â»The adapter makes this noise even if the pod isn't hooked up.I can just change to the pod source and turn the volume up on the hu and I get the whine.One thing to try- on base audio systems like mine, nothing normally plugs into the 12-pin connector. In the M&Ts, however, I believe there is a 12-pin plug. (This is without XM; having XM or OnStar would require a 12-pin plug.)If you had a 12-pin plug, and you plugged the IPOD2CAR harness in between the existing 12-pin and your radio, this could be the source of the noise. It could be a ground loop, or something coupling noise in. If this is your situation, I would suggest to try unplugging the original 12-pin from the IPOD2CAR harness, and leaving the IPOD2CAR connected to the radio. See if this eliminates the noise. If so, then now you know where it's coming from. What to do about it is another story, though.....If not, then you could try the power filter as jahntassa suggested.

dan326 · Post by **dan326** » Wed May 18, 2005 9:55 am

Well I am still having a problem. It is not as noticeable, but there none the less. Here is what I have done since I last posted. Here is the tech brief.I talked to a guy at peripheral. He told me that there is a harness modification for the GM3 harness (that is the harness that I had to use, and it has no ground wire). This modification cuts the thin wire found in slot 11 on the 22 pin that plugs into the adapter. The stub that remains must be lengthened and grounded. I grounded it to the chasis. The remaining wire in the harness bundle can and maybe should be capped/ insulated.This does help to some degree, but the noise is still present when the volume is high and there is an absence of music (pod is paused or song has low sound). Needless to say, I am starting to get a little frustrated and am thinking that I am going to have to learn to live with it.I did send a contact to tech support at peripheral and he will send me the next trouble shoot. In the mean time any experiences you are having, please share.

Attached files PXHGM3TechBulletin[1].txt (2 KB)

Jahntassa · Post by **Jahntassa** » Wed May 18, 2005 10:22 am

Did you ground it to the radio itself, or the chassis of the car? You'll get the best result if it's on the radio itself.Also, if you have no music playing, and the volume all the way up, I'll almost guarantee you'll have noise. The question is whether or not you hear it with music..

dan326 · Post by **dan326** » Wed May 18, 2005 10:43 am

It is actually grounded to a screw that is behind the glove box. There is no paint or anything on the screw. If I was to ground to the HU, what color is the gound wire? I do hear the noise when there is a soft spot in the song( not much music).By the way, I thought you mentioned you had an adapter. If that is true, do you have it grounded to the radio?

Jahntassa · Post by **Jahntassa** » Wed May 18, 2005 8:43 pm

I got tons of noise when grounded to that particular screw.I took out the headunit and unscrewed one of the screws holding the side bracket to the radio, and used an o-ring to attatch the ground wire to that screw. Basically, grounding it to the radio.If you connect that ground physically to the radio, it should help. I have an aux-in adapter, and yes, it is grounded to the radio. Any other place gives horrendous noise

GMJAP · Post by **GMJAP** » Thu May 19, 2005 12:51 am

The radio ground is a brown wire in position A12.Did you ever try removing the 12-pin? (That is, the original 12-pin from the back of the GM3 harness?)Also, my MP3 has a lame headphone volume level, so I normally have the head unit turned up to 80% or so of max volume and don't hear any noise.

dan326 · Post by **dan326** » Thu May 19, 2005 9:47 am

The problem with taking the 12 pin out of the harness is that the radio doesn't think the xm exists. I then can't use the adapter because when I change the source using the band button, all I get is fm and am.As for the volume issue, adjusting the volume on my ipod does nothing.

dan326 · Post by **dan326** » Thu May 19, 2005 9:59 am

I tried to ground the adapter to the radio harness as you suggested. That really didn't do anything. The noise is just as bad if not worse. So I am starting to wonder a few things.First, are you using the GM3 harness? Or are you using a different harness?Second, if you are, did you make the adjustment to the gm3harness to create the ground wire in order to connect it to the radio?Third, is it possible for there to be a problem with my gm3 harness? Should I try a different one?Fourth, is it possible for there to be a problem with the way I have hooked up my power wires. To recap, the power wire from adapter is twisted to the power wire from the radio on one end and the stump from the HU is on the other end. This hook up looks like a y.Fifth, do you think that this harness modification that I have attached will work and is worth the trouble.

Attached files GROUNDLOOPFIX-IPOD2CAR-DIAGRAM[1].txt (1.4 KB)

Thoughts on eliminating ground loop in ipod2car

Thoughts on eliminating ground loop in ipod2car

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