BT4000U initial power issue

[nightmare080584]

Hi all

After having had another manufacturers brand of head units i have returned to Sony for headunits and got myself a MEX-BT4000U for the bluetooth and hands free option to fit into my BMW "57" plate 3 series E90.

Having connected it correctly using various harnesses for audio, steering wheel stalk and reverse beep thingy and used the extra long yellow 12V constant cable from the unit to the fuse box for a constant 12V connection, I have stumbled upon another very odd phenomenon.

After leaving the car overnight or even a couple of hours when i go back to it and try and use the headunit it turns on very briefly (say about 3 seconds) enough time for it to show just "TUNER" before beeping once and turning off, if i try and turn it on, it will only turn on briefly before turning off again.

I have to wait about a minute or two before trying again and it will then work normally, why does it do this??

[Drumzman]

Hi nightmare080584,

This does sound a bit odd!  The only thing I can think of is that it might be something to do with how the car provides power to the stereo.  Usually you have a switched 12v supply that turns the unit on and off with the car's ignition (red wire to the stereo and sometimes called an 'accessory' position), and a permanent 12v supply (yellow wire to the stereo) that backs up presets on the radio, clock settings etc etc.  However, some cars don't have an accessory supply, or even sometimes the permanent and switched 12v supplies are the opposite way round on others.

Consequently, there are a number of correct but alternative ways you can wire up your stereo depending on the vehicle you're installing it to.  I've included a diagram that shows the choices below.  It might be worth trying the different ways (you can't do any harm but only one will probably make the stereo behave as you would expect).  I wonder whether the option connecting both the red and yellow wire of the stereo to a permament supply from the car might be best for you - the only downside is that you have to remember to use the power button on the stereo itself when you leave the car.

Don't know if this helps?