I have a 750il stereo system...

[shogun]

Front panel

The aux plug hole is at the right side bottom front face

This one is for the rear armrest. There you cannot see the hole in the front for the aux plug. It is underneath and you can plug in from the area where the storage shelf for the armrest is.
That is the difference.
You must make sure that the speed indicator cable is connected. Otherwise it might stay on mute or telephone sound = no sound at all.

I had the problem last summer. No sound at all. All was frozen and it showed volume 5 and aux, but I could not switch anything, no sound at all.
Changed front and rear panel against other ones from a friend, nothing changed. Brought it to Sony with the complete set in the trunk. They could not find anything. Installed it again, after someone recommended to put the into the refigerator for a day, and then it worked again. It was the too high humidity during raining and Taifun season which caused this. Already had this twice in several years always during raining season when we have >90 % humidity.
Here is some info from OJ in Norway, but his audio can be different from yours.
http://ow.no/index.php?option=conten...d=56&Itemid=43

I do not know much about audio equipment, sorry. Maybe there are other experts here.

[Whit]

Thanks! Crazy thing is, mine only works (and lights up) with the back piece in the front dash and nothing connected in the rear armrest! I don't know. The seller had the entire system and wiring pulled and tested. Maybe they reinstalled the cable backward front to rear?
Well, the remaining unused rear piece (or the cable) may have a short. In addition, the CD changer loads but will not read the CD. I think it is just a dirty lens. I will clean it and see.
The system is working on all speakers and I can control it from the front, but I hope to get it to control everything from both front and rear one day. I would be willing to trade the whole setup for non-original equipment that has front and rear controls. Anyone? Maybe someone wants the 1988 750il factory system? In the Philippines, my wife and I have a driver, so it would be nice to have control from the back.
Here is a tip on the "frozen" radio display or volume control: first, just turn the car off and get out. Wait about 60 seconds and get in and restart the car. That "unfroze" mine, so it might work before pulling it and chilling it.