Steering wheel controls not working d40

[dpenfold01]

I have recently relocated my head unit under my passenger seat in my 2010 d40 st and doing so required me to wire about 40 different leads. I have got the head unit running perfectly apart from the steering wheel controls... The problem is the volume down toggle works but not the volume up. None of the other buttons work when controlling the radio. However.. the bluetooth button does work and when I am in the bluetooth settings I am able to use all the buttons functionality's.

I have run continuity checks on all the wires and they are all connected and have checked all fuses and they are all fine.

Could there be a problem with the Bluetooth module which is hidden behind the dash? can I bypass this module straight to the head unit.

cheers

 

[Old.Tony]

I think we can safely say that not many of us have ever tried to put the head unit under the seat where it can't be seen, so you're in unfamiliar territory anyway.

The first thing I would wonder about is the voltage levels over the length of cable. You can't be using thick cables, and thin stuff just demolishes volts over distance. Could it be that the signal from the switch is "too faint" ? Remember that there's a thin wire carrying the test voltage down, and the return line should show testV minus small loss, but if it's any less, the system may assume it's not there?

Could the bluetooth unit look at the return voltages differently?

The only real way to see the drop is to put 5V on one end of the cable, a small load on the other, and measure the voltage on both ends.

The only way to fix that is to shorten the cable or go larger.

I could be bonkers here - doesn't make sense to watch the wire, see it rise up to (say) 3V and ignore it because the "trigger" point is 3.5V just because that caters for V-drop in the max line length from steering wheel to head unit, but it's a possibility.

Wouldn't be the first thing we've seen in cars that hadn't made a whole lot of sense.

Worst case scenario: we'll start talking about the idiot idea I've raised and come up with the real answer.

 

[dpenfold01]

Yeah it's a little project of mine, what I have done is placed a nexus 7 tablet in the double dins location, which is now my media center. fits perfectly with little to no modification of the car so future resale shouldn't be a problem. I could post a few photos if you would think the crowd on here would be interested?

I do see where you're coming from with the voltage drop. I did a few quick calculations and with the new wire I have installed a voltage drop of approx. 0.2V which could possibly be enough. I will test that theory by disconnecting all the wires for a 3rd time and connecting directly to the original harness acting as if nothing has been changed.

I do have my suspicions that it is something to do with the Bluetooth module as I believe the steering wheel controls connect to that then the radio which could mean it it blocking the flow so to say.

Lets hope it's a matter of thicker/shorter cable

I'll let you know the outcome and see if we need to try some more crazy ideas.

Cheers

 

[dpenfold01]

So I have spent the past hour disconnecting and reconnecting the harness to what the length was before I cut the harness. To no avail though the volume rocker up and channel selection buttons do not work with the radio still and the channel selections still work with the bluetooth which is leading me more towards a broken bluetooth module.

Would you have any idea how much I would pay for one of these or whether I should try a wreckers or something?

Cheers

 

[camo.b]

I did a conversion on my thai kingcab.installed the older buttons to use with a carpc...i found that it had 2 or 3 diffrent circuits in the button board..ups downs and the two other buttons....all were based on a resistance value..i had to resolder the smd resisters on the button board as they were too similar for my windows 7 software to see the diffrence between the buttons...not that this direcly applys to you but they are a resistive button board so no voltage runs thru them..check the resistance values from the input under the steering coloum and the output pins in the same place...then check the value after the bluetooth module...then after the extended lenght of wires you added...

 

[camo.b]

They all need to match the value at the bluetooth module...the values are important as a slight variation could be the diffrence between a working setup and yours..