Guide: Pioneer radio control without interface

[ronj]

I'll describe here what I did to get the radio-stalk behind the steering wheel of my phase 3 to work with a Pioneer radio without an interface.

Warning: this particular guide will only work with a two wire stalk. The five wire variant will be easier since you can make a small adapter board. I will not describe this here but consult me if you want help with that.


You will need:

- A collection of Torx screwdrivers
- Soldering iron suitable to solder electronics (fine tip)
- Decent solder
- Cutting pliers
- Sharp (Exacto/Stanley) knife
- A multi-meter (or something with the function to measure resistance in the range of 1K to 22K)
- 8K, 4K, 4K and 6K resistors (or something close) 1/4 watt, 5% metal-film is fine. Nicest would be to have 2x 4k and 6K resistors as SMD 1206 because then you can simply replace the standard values.
- 3.5" jack plug. Maybe salvage this from an old Walkman (or MP3 player for the younger generation).


Step-by-step guide:

First off remove the cowling around the steering wheel column where the stalk is located (I believe there is a detailed guide around somewhere).

Remove the three Torx screws in the bottom of the cowling. Two on the front one on the back.
Move the cowling downwards and towards you to remove. Note: the cable of the steering wheel control stalk is still plugged in so you can not retrieve the cowling just yet.
Remove your head-unit and find the steering wheel control cable. Unplug the yellow connector and carefully guide it out behind the dashboard. Now retrieve the bottom cowling.
Unscrew the three Torx-20 screws which secure the stalk to the cowling.

You now should have the stalk removed like this:





Dismantle the stalk.

Now would be a good time to turn on your soldering iron and let it heat up, if it needs to.
Carefully prize loose the clips that secure the two half's of the steering wheel control with a small screwdriver or your nails.
Retrieve the cover and take care since the stalk itself is spring-loaded so the spring could pop out.


You now should have something that looks like this:





If everything is still in its original place you can now remove the stalk with switch (the white thing). Don't lose the spring!
Next up you can retrieve the green circuit board.


Resulting in something like this:


    


Now its time to solder the 3.5" jack plug to the cable.

Cut the yellow connector from the cable as close to the yellow connector as possible to leave enough room to solder the jack-plug.
When you have a new jack-plug that consists of several parts dismantle it and make sure the parts that should be on the cable before soldering are there.






Strip a bit of the wire to expose the copper for soldering.
Solder the white wire to ground (bottom ring) of the jack-plug. If your jack-plug has a tension relief for the cable I find it easiest to use that to hold the cable in place while soldering.
Solder the blue wire to the tip of the jack-plug. You need to measure with a multi-meter what connection this is, it should be the shortest one.



    

    
I like the new jack-plug solution since it gives a nice OEM look. When you don't have a new jack-plug just solder the wires together, measure to make sure what wire is what. And isolate with some shrink-tube.






Using the correct Pioneer functions.

In principle the stalk will now work, but every function of the switch will turn your Pioneer off. Since this is not what we want we have to modify the resistor values on the PCB to select the correct Pioneer functionality.


The functions we are interested in are as follows:

Track +        8K Ohm
Track -       12K Ohm
Volume +   18K Ohm
Volume -    22K Ohm

The keen reader will see a mismatch between these values and the resistor values I mentioned in the list at the top. This is because the PCB switches the resistor values in series. We need to find values that add up to the values in the table above.

In the stalk the first function is signaled by a short circuit so we need to solder a resistor in-line with the white cable.
De-solder the white cable from the PCB. I typically do this by using some pliers to grab the wire close to the PCB, heat up the solder and carefully move the pliers away from the PCB. No burnt fingers and remove some of the excess heat by conducting it to the pliers.
Solder the 8K resistor in place of the white wire and solder the wire to the other side of the resistor. Isolate with some shrink-tube (ideally glue lined).

Now comes the tricky part in case you don't use SMD resistors. The housing is barely large enough to fit the extra three resistors.

Solder, in series with the first SDM resistor, a 4K resistor (see picture for details) and make sure you can "fold" the resistor over the top of the PCB.
Cut, with a sharp knife, the PCB trace between the two solder joints of the resistor you just added. Measure the resistance of the track to see if you cut deep enough. It should measure 4K.
Solder the 6K resistor in series with the second SMD resistor. Again cutting the PCB trace between the two solder joints. You can see this on the picture above.
Use a piece of scotch tape (or something similar) to isolate the top half of the PCB under the added resistors to prevent short-circuits.
Whey you don't measure open-circuit when the stalk is in it's neutral position it is likely that a short circuit here has caused the problem.


The result of the above should be something like:





Solder the last 4K resistor at the bottom of the print such that it can slot in the hole in the enclosure. You'll need to bend it a bit when re-assembling the housing. Again cut the PCB trace between the solder joints.

Now place back the PCB in the housing. Be careful not to cause a short circuit by exerting pressure on any of the added resistors. It is probably necessary to cut some pieces of the housing to make extra room.



    





When the housing is closed its time to check all switch positions. You should measure open-circuit when the switch is in neutral and somewhere near the values in the table above when selecting the different functions on the switch. If you measure the same resistance twice or something else is wrong, carefully check your work with the multi-meter.


When you measure the correct values: assembly is the reverse of removal . Job jobbed!


Note: because the way Pioneer has specified its resistance to function values the functionality on the stalk is reversed corresponding to the print on the stalk.

Note: when you use SMD resistors (why do you need this how-to?) you must not cut the PCB traces!

Good luck!

[cully]

good guide thankyou

[tigerstyle]

Presume the Ohm range for the headunits is fixed to Pioneer? (but other brands would be similar?)
Googleable information if it's needed right?

[ronj]

Yes that is right, the general system should work for other brands as well. I even think Sony is compatible to this exact resistor value specification but have not yet verified that.

[Eeyore]

great guide! thanks x

[righi]

Hey! Just removed mine and its the 5-wire version, can anyone help me out? Thanks