lights stay on in head unit; no sound. While driving it will come on only to go out some time later. Sometimes it does not work when 1st starting the car, head unit light are on and dash indicates what station is playing buy no sound...where to start?

 

I see that nobody has replied yet, so, hopefully I can be of assistance.

[Disclaimer]:Let me start off by informing you that I am not a professional by any means, and anything that I suggest should only be taken into consideration at your own risk. I am not to be held responsible for any problems that are incurred. I am simply trying to help you solve your problem by using the information I have found by researching the problem, and dealing with similar issues. Thanks.

Here is what I have found for you so far that may be helpful. I will provide you with these links and then give my own opinions on how to go about troubleshooting. They don't relate specifically to your problem, but they may be helpful.

Links:

Bose sound system not working - FixYa

A4 (B7) BOSE & Rear Sub - No Sound

:: a4mods.com :: - The Premiere Audi A4 Modification Guide and Pictures Library

Does the sound cut out in all speakers at once? When they do go out, do they make any strange noises (i.e. popping, buzzing, whine, etc.)?

From what you have said so far, I would suspect that either one of your connections is loose, or your Bose amp is going bad. Let's hope it's simply a loose connection.

With the Bose, I believe all of your speakers are powered by the same amp; your amp should be located behind the passenger's-side rear trunk panel. In my car (2005 Audi A4 1.8T non-Bose), only the rear speakers are powered by a rear amp; the front speakers are powered by the head unit (I discovered this when I recently installed a Pioneer AVH-P2300DVD).

Do you have the factory head unit currently installed? I am assuming that you do.

You should always disconnect the negative battery terminal when working with electrical components (to be safe), but that's your call. I would begin by pulling out the head unit (if you have never done this before, it involves using four removal "keys" that may be purchased on Ebay for very cheap, or even carried at your local Walmart in the car audio section), and making sure that everything is securely connected to the back. The removal of the head unit is fairly simple, but it can be tricky sliding the "keys" out.

It will look something like this when removing it:

http://rds.yahoo.com/_ylt=A0PDoX8g8D...s/IMG_1128.jpg

Assuming our cars are generally the same aside from the Bose, on the back of the head unit, there will be three harnesses: two black, and one brown (one of the blacks will be the same size as the brown; the other black is for the Bose amp), and two plugs (one is for the car's antenna, and I believe the other is an input for satellite radio--these will be left alone anyways). Unplug the black harness (part of which is used for the Bose amp/speakers), and plug it back in. Then, try turning the ignition on, and see if you get sound.

Here is the diagram for those harnesses to give you an idea of what I am talking about (this label is from the head unit of an Audi A4 B5 non-Bose car, but I believe the label itself is rather universal--your head unit will have its own if you would like to verify that):

http://www3.telus.net/~dougkong/Audi/Symphonyrear.jpg (disregard circles)

http://rds.yahoo.com/_ylt=A0PDoS.fBj...unitwiring.jpg (somebody has labled this one)

The one I suggested unplugging and re-plugging, insuring that it's secure, is the bottom one. Just to explain that a little further, if you look at the "line-out" section, you will see why this is the harness that, if disconnected, would cause your loss of sound to all four speakers. On my car, the [+] was for the remote wire to power the rear amp, and the "comm." was for the ground (common ground). Then, the pre-amp connections of course, RF = right front, RR = right rear, LF = left front, and LR = left rear. For your car, assuming that all four of your speakers are powered by the Bose amp (rather than just the rears, like mine), this disconnection would cause loss of all sound.

After you have tried what I mentioned above: if you get sound the way that you should, then great; problem solved. If not, then it's probably your Bose amp that has gone bad. Good luck. Let me know how it goes.

 

Sorry for this dumb question, but if I have a loose connection on the BOSE plug, what's the best way to confirm this? Is there a way to tighten the wire connections inside the connector that plugs into the back of the head unit?

I purchased a reconditioned head unit from ECS Tuning for $35 with the hope that the problem was in the head unit. It seemed to work at first with the new head unit, but now I'm back to no sound out of the left channels, both front & rear.

Because it worked when I first plugged in the new head unit, I'm guessing that it's a loose connection in the wires on the plug.

 

By "it seemed to work," do you mean it did for a short period and then stopped; or are you unsure of whether or not it worked at all? If it didn't work at all (even with the new head unit), then the head unit probably wasn't the problem. It may have been a loose connection all along, or it could be an amplifier issue. It's important to always rule out the simple solutions before the complex so that you don't waste time (and, potentially, money).

The tab on the side of the harness should click into place once inserted into the other. If you look on the side of the harnesses, you will notice that one has a ridge, and the other a depression for the ridge to fit into; along with that, there should be a small plastic tab that locks into place once the ridge and depression are fitted together (when the harnesses are pushed together). To release the harness, you typically have to depress one of the tabs in order to unlock the ridge from the depression before pulling the two harnesses apart from each other; if it comes undone without needing to depress the tabs, it's probably loose. Your best bet would be to just press the two harnesses together with as much pressure as you can apply without damaging anything. If it's still loose, the tabs have probably worn down and you will probably have to buy a new harness (or harnesses).

You may also want to check to make sure that all of the actual pins inside the harness are there and unbent/undamaged. I am assuming that the head unit you purchased was compatible with the Bose installed in your car? I believe the Bose and Symphony head units have the same harness that plugs into the head unit, only slightly different pin layouts in the actual harness itself; that could be the problem as well (unless you definitely purchased another Bose head unit).

You may also want to check the fader controls and see if adjusting them changes anything.

 

Yeah, sorry for my vague previous post. I'm not an Audi noob, and I have experience changing out head units. What I meant to say is that it worked initially when I changed out the head unit, but then it went back to not working after the next time we started the car.

So, my thinking brings me to either loose pins on the connector on the back of the head unit, or a bad amp. I know I got the connectors pushed in and clicked, I've done that many times and I double-checked that as the first trouble-shooting attempt.

How does one repair loose pins on a connector, assuming that's the case?

Is there a known way to check the amp itself to test whether it's outputting power to all channels?

Thanks for the help!

 

I have heard of the amp making a high-pitched whining noise when malfunctioning.

To test whether or not the pins are getting power, you will need a circuit tester.

Something like this:

http://rds.yahoo.com/_ylt=A0PDoTFRiD...52060webd1.jpg

You put the positive end into the pin slot, and then you put the negative end to a ground. If the light comes on, it has completed a circuit (thus, it is getting power).

Refer to the label on your head unit; it provides a diagram of the pin layout for your wiring harnesses.

Something like this:

http://carstereohelp.net/images/Wire...diA6122301.jpg

If you look at the picture I provided, the harness you are having trouble with is the very bottom one. Look to the far right where it says "RF, RR, +, Com., LF, and LR." Test whichever side you are having trouble with. I believe you said the left front and rear? Hook up the circuit tester to the LF and LR pins (female pins) in the harness (the OEM harness wired to the car itself).

Once you determine whether or not the (female) pins are getting power, you will know whether or not the amp is supplying power to them. If they are loose, they probably wouldn't be getting power. It's possible that one of the (male) pins is bent (on the head unit's Bose harness), but you should be able to tell just by looking at it.

If you have to replace one of the pins, they make removal tools for them.

Something like this:

http://static.scan.co.uk/Images/Products/1044196-a.jpg (this is a picture of a Molex pin removal tool)

Replacing it should be as simple as removing the old one, and setting a new one in place using the removal tool (for the female pins). The male pins (which would be on the harness that plugs into your head unit), on the other hand, those would be tricky; if one of those is bent, your best bet would be to buy a new harness.

Audi Radio Wire Stereo Wiring BOSE AMP Harness Connect | eBay ($16.50 shipped) -- replace only if one of the male pins is bent...

 

thanks for the input...all speakers go out at once, no popping, come back on. I can hear the amp switch when powering on/off. No loose connections as I have pulled both the amp and head unit...will try pluggin in an amp if I can find one to try...

 

I really appreciate the time you've taken for a full, detailed answer, subtlemastermind.

I haven't dug into getting out the circuit tester yet, but I did find the Bose amp in the back, and I disconnected/reconnected the plug from there. So far, so good. I've had sound from all speakers since I did that. Dunno if it's going to last for long, so we'll see. I've got my fingers crossed!

 

You're welcome. I'm glad to hear that you have (hopefully) solved your problem.

 

yea happened to me one time. took it to dealership to be told just needed amp replaced and Done.