Aux input drops out randomly when connected
 

I installed the Aux input cable on my 2004 X5, without dsp, without navigation.
I then proceeded to connect my iphone to test it out. It played fine...for a while anyway.

The first time I use it, the stereo will stay on the aux input mode and play from the iphone perfectly, and then at some point it will drop and switch to the radio. Pressing "mode" will not get the aux input back. If I disconnect the iphone, I can then go back to the aux input and play the iphone again, but this time for only a minute or so max before it goes back to radio and Aux is no longer available.

If I simply leave the cable unattached to the iphone, the radio will stay on Aux indefinitely...no issue whatsoever.

Any suggestions on how I get the iphone to play? I have tried an iphone 4 and 5, but have not located some other device to test it with besides the iphones.

Thanks!

Mine does this too. When my friend plugged his ipod in, it did it fairly consistently. When I use my android phone, it does it but only randomly. It seems to happen more often when the phone is plugged into a power source. I can only guess that the phone is sending some sort of signal up the aux cable that is confusing the car's radio. Maybe the fact that the phone's aux connector can use a mic as well, I don't know. I haven't found a solution. I thought it might be the connector on the back of the radio coming loose, but I checked and it was totally fine.

Is this a common issue for most everyone using the aux input?? If so...why hasn't it been brought up as one of the con's for using it over bluetooth? In all my searches I didn't see this brought up anywhere.
Would be nice to find a solution...

Aux input drops out randomly when connected
 

:iagree:Count me in as one who has this (maddening) problem. 2006 E53 here with non NAV and I too retrofitted the Aux cable to connect to the CD/radio head unit, and ran it to plug for my iphone/ipod next to cig lighter. I will have iphone plugged in, Aux displayed and all working fine, until it suddenly cuts out and switches to CD. My new obsession is listening to Podcasts from my iphone and of course volume turned way up to hear better, and then suddenly switches from Aux to CD and (as George Carlin said) IT'S THIS LOUD! This has been happening for over a year, sometimes I can get through hours of iphone listening w/no problem, sometimes it happens after 5-10 minutes. No rhyme or reason. I often do have the phone charged in the lighter while Aux is in headphone jack, as OP said maybe this is the problem? Funny I never thought or noticed if that was the case ( that it switches off Aux suddenly b/c also connected to power source). I will try it with and w/o and see what happens.

Wish I could offer a solution myself. Getting tiresome to play this game where I try and quickly lower volume as soon as I see the Aux switch over to CD!

What I've noticed recently is that this only happens when my phone battery gets to 100%. Is that the case for you guys as well? I've been able to reliably prevent it from happening just by unplugging the power cord.

this happens to mine as well the problem seems to be only when I have the phone (Iphone 5s) charging it also happens with my Ipod as well as far as I can see it is a ground issue because the random switching happens less frequently when I have my phone plugged into the rear cig adapter

The AUX source may not be "sticky" enough to hold the input.
Try a 300K Ohm resistor between the + and - audio line.

Fix for AUX input dropouts
 

I just installed the AUX kit in a 2004 Z-4 to listen to a portable Satellite radio.

It worked great for about an hour and then the AUX input on the radio display would disappear and it would switch to an FM station.

The only way to get the AUX mode back was to unplug the audio cable from the Sat radio.

This happened several times after that - sometime immediately, sometimes after 5-10 minutes.

I could recreate the issue using a Motorola Droid phone on internal battery or on vehicles 12V accessory port.

The BMW AUX cable has a small circuit card built inline. The card contains 2 ccapacitor in series with the l/r audio signal which blocks DC and allows AC (Audio) to pass. It also has a 300K ohm resistor on the Radio side of the Caps. I believe that this resistor is what allows the radio to automatically "detect" that there is an AUX input jack wired into the car.

So here is what could be going wrong - 1) There is a ground loop (grounds at slightly different voltages) between the radio and the audio device that at times is sufficient to swamp the very small voltage or current used to sense the 300K resistor. 2) The audio output of the radio/MP# players etc. are designed to drive headphones which have a impedance of 100-300 ohms ish. The AUX line in is likely a much higher impedance so there is a mismatch and the low resistance messes up the AUX sense circuit in the radio and causes it to drop hence the failures when the phone was NOT connected to vehicle power. 3) The radio is expecting a differential signal and the audio devices typically provide a signal referenced to ground and not another signal line.

So what can be done?

The best way is to "Electrically" isolate the audio device from the radio AUX input. If isolated there can be no ground loops or differential input issues.

Transformer isolation is ideal as the circuits are magnetically coupled but not electrically coupled.

I researched and purchased a product made to do this - a "Stereo" Pac-Audio SNI-1 3.5 Ground Loop Isolator. Pac-Audio.com Link The cost was $19.95 at the local car audio shop.
It comes with standard 3.5mm jack so no wiring is necessary - just plug it between the audio device and the AUX input.

http://pac-audio.com/UserImages/SNI-1%203.5.jpg

So far so good. I drove around WITHOUT it in circuit for about 20 minutes until the AUX dropouts started. I plugged it in circuit and have driven for several hours with NO, NOT ONE, AUX dropout with Sat radio or phone.

There are other makes and models of "Noise" filters, ground loop isolators etc. If you get another make just be sure that it is TRANSFORMER coupled (the KEY) and is not using lower cost RC filtering. Also make sure that you get a "Stereo" version or you'll have to buy two!

Also, I couldn't detect any difference in the sound quality even when I had the convertible top fully closed and my hearing aids cranked all the way up :whistle:!

So, after 15 years, this has begin to happen to my Sky-Fi sat radio and factory non-nav radio AUX too... the AUX doesnt show up in list, then sometimes when I unplug the 3.5mm sat radio source cable and then plug back in, then the AUX shows up, and plays for a few seconds, then radio switches to another source (radio/cd). so odd.
I have also been having funky things happenning to my sat radio too to make me think I've needed to buy a new one after 18 years of use... so perhaps it IS just a sat radio issue and not a BMW/wiring issue. I'll have to investigate using another music source.

Hopefully, I may have a solution. I have a harness to turn the CD option to Bluetooth. If I have time this weekend, I'll install the harness. It plugs inline with OEM CD connectors. I found the inline harness on ebay.