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Power for bluetooth receiver in glove box

7K views 13 replies 3 participants last post by  rudeney 
#1 ·
I have embarked on a project to install a Bluetooth receiver module in the glovebox. Currently there is a CD changer, and an existing 3.5mm jack in the glove box which I used to feed the audio in to AUX. I needed power for the Bluetooth module so I figured the CD changer must have power going to it. Which it does, but I am not sure if it's switched 12V. The 3-pin power connector has red/blue, brown, and brown/blue wires. Using a multimeter (without the key in ignition switch) I register 12V between the red/blue and brown. I also register 12V between the brown/blue and brown. I T-tapped the red/blue and brown wires for the Bluetooth module. Everything is OK, however, I don't believe the module loses power when I park and move away. I then guessed maybe the red/blue is always hot, and perhaps the brown/blue is switched. So I used the brown/blue and brown for the Bluetooth power and the module gets no power at all. Not sure why since the multi-meter shows 12V on that same pair. Anyhow, long story short, is there a 12V switched power in the glove box off the CD changer that I can use?

For reference, the power connector looks just like the one here: http://mbworld.org/forums/attachmen...view-mercedes-benz-cd-changer-pinout-1-2-.png
 
#2 ·
I cannot lay my hands on the 12v distribution circuits, but reference to the fuse information shows that in Rear SAM (N10/2) fusebox, fuse f20 carries 12v to the glove box CD player. This is on circuit 30, which is the Unswitched power line - i.e. it is always live.

Also be aware that if you remove a module from the D2B bus ring, unless you insert a bridge connector, other items on the bus will not work, e.g., radio, COMAND.
 
#3 ·
Thank you for the info. That seems to corroborate what I am actually seeing. Oh well. I guess the BT module will always be on...

I would be interested to know though why there seems to be 2 12V lines going to the CD changer and how they differ... I still have the mystery of detecting 12V on the blue/brown and not being able to power up the BT module on it as well.

Ps: I am not disconnecting the CD changer. The power and fiber cables continue to connect to the unit.
 
#7 ·
I think that you will find that all the fuses in the cabin fuasebox (F34) are on circuit 30.

The OP will have to use N10/1 fusebox to find several fuses (f48 to f51) on circuit 15. These only have 12v power when the ignition switch is in position 3, after engine start.

Check out the W209 CLK fusebox details in the thread listed in the W209 forum sticky.
 
#5 ·
The BT module has a 2A fuse on its positive terminal... So fusing is not an issue. However, I am not familiar with tapping into any fuse panel. 1) Does that require removing the glovebox in my case to gain access? 2) How does one tap into the fuse panel?
 
#6 ·
The cabin fuse panel is on the end of the drivers's side of the dash. Open the door and remove the panel on the end there. These taps, available at most auto parts stores, are great for this sort of job:

 
#8 ·
An afterthought for those wondering how modules with unswitched power do not drain the battery when the ignition is switched off....

I'm not too sure myself, but I have noticed a common signal called 'wake-up' that is widely distributed, so maybe that is used to enable the module to power up. Can anyone confirm this?
 
#9 ·
I fixed my WIS and I can now take a look at your CLK350 CD changer power wiring. CLK 350 uses MOST bus.

Circuit for A2/6 shows:

pin 1 (red/blue wire) from circuit 30 (Unswitched 12v)
pin 2 (brown wire) to circuit 31 (chassis earth)
pin 3 (blue/black wire) from X30/8 (wake-up signal to CD player)
 

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#10 ·
Yeah, I forgot about that. I had a BT hands-free speaker on my CLK that I wired in this way, then stuck to the A-pillar, but I had to manually turn it on and off.

As for the "wake-up", I think that is usually CAN bus controlled.
 
#11 ·
Thank you for the document and information. So it seems the CD changer tap idea is indeed SOL if switched power is needed. Now, I am not too keen on pulling a tap all the way from the driver fuse panel. Is there a switched power cable I can tap into in the vicinity of the glove box?
 
#14 ·
Remove the top wood panel (or maybe metal, if yours has that option) on the center console, then remove the ashtray. You'll find the wires going to the lighter socket there. Use "vampire taps" to tie in. If you need good instructions for removing that paneling, search the forum - maybe under "radio removal" as these are the first steps for that and I know there are several good DIY docs for this that have been posted.
 
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