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Steering wheel controls with aftermarket headunit

Discussion in 'Gen 2 Prius Audio and Electronics' started by brettray, Oct 31, 2005.

  1. brettray

    brettray New Member

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    Summary: PAC SWI products do work with Prius.

    I recently upgraded my whole sound system with a new deck, amp, and speakers. One of my goals was to keep the functionality of the steering wheel controls. To do this I used a third party product to translate commands into the decks language.

    Pacific Accessory Corporation makes a line of products designed to utilize factory steering wheel controls for non factory head units. The SWI-X uses IR to send commands, but they also make different versions to work with specific brand stereos. I have an Alpine deck so I installed the SWI-ALP which sends commands via a cable that plugs into the back of the deck.

    The Prius steering wheel controls work by connecting two wires with a different resistor value for each button. For example if the volume up button is pressed an ohm meter on the wires will read 2 kohm, and if the next track button is pressed the meter will read 1.5 kohm. If no buttons are pressed the wires are an open circuit. The PAC products detect this resistance and translates it into a command for the new head unit.

    I managed to get the SWI-ALP working yesterday after a good bit of trouble shooting. The directions were for the most part quite clear. They identified which wires were relevant using a drawing of the existing plug and pin numbers. The process involves connecting the signal wires (two) to the PAC-ALP, one wire via a resistor. Then Power and ground must be connected and you’re done. The part they did not make clear was that in the Prius the signal ground and the power ground are not connected. I fist connected the units ground wire to the signal ground, at which point the unit did not turn on because it did not have a closed loop for power. I then tried connecting the ground wire to the cars common ground, at which point the unit turned on but did not recognize any input. I made it work by connecting all three wires; common ground, PAC unit ground, and Prius signal ground.

    It was then an easy process to program which button does what. The bluetooth (hang up/Answer/voice command) buttons are part of this system. I lost their functionality when I removed the JBL Head Unit so it was good to be able to use them for this. Most mappings were obvious but some were not. I used the voice command button for mute and the answer and hang up buttons for next/previous folder.

    The buttons are not as responsive as they were with the JBL System. I have to hold the button down for longer then feels normal to get an effect. Pressing and holding still works, however, for things like large swings in volume.

    Overall I would recommend the PAC SWI products to any with an aftermarket head unit.
     
    #1 brettray, Oct 31, 2005
  2. tmorrowus

    tmorrowus Member

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    Thanks for the report. I wonder if this thing would work correctly if I wanted to have some of the steering wheel buttons continue to operate my JBL head unit, while having other buttons go to an aftermarket Alpine deck. I'm thinking of removing my amplifer, controlling volume with an Alpine deck that gets the signal from the factory system. It sounds like that would work okay and I could use the steering wheel volume for the Alpine but the track buttons for the JBL head unit.

    So you didn't have to disconnect the steering wheel controls from wherever they are normally connected right? I'm assuming you just tapped in in parallel?
     
    #2 tmorrowus, Oct 31, 2005
  3. brettray

    brettray New Member

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    I am not sure if that would work. I have removed the JBL system (amp & head unit) entirely. The new deck now sits in the center of the dash where the JBL unit used to sit. For me the SWI is connected directly to the steering wheel controls without anything else in parallel. I believe that both units might be able receive input as long as the JBL head unit showed a constant resistance between the signal wires and ground. The PAC SWI can be programmed for different resistance ranges so that it can be used in different cars, but in this case that would allow it to work with another resistance in parallel to the switches.

    The hard part is getting the two devices to share. It will be easy to make the SWI ignore the buttons that you don’t want it to control, but I don’t see any way to keep the JBL deck from receiving the volume signals, as all the switches except the source button are on the same line.
     
    #3 brettray, Nov 1, 2005
  4. tmorrowus

    tmorrowus Member

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    I assume your climate control steering wheel buttons still control the car's climate system, right? So it seems likely to me that there must be something else in the car reading the steering wheel controls at the same time as the JBL radio or PAC SWI is reading them... indicating that parallel connections work. I'm assuming the devices that read the controls have very high input impedances (resistances in this case) to allow parallel connections. Unless the climate controls are on a separate circuit.

    As far as the sharing that shouldn't be a problem since when I disconect the JBL amp the JBL head unit volume controls get disabled.
     
    #4 tmorrowus, Nov 1, 2005
  5. brettray

    brettray New Member

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    Good Point about the amp and volume control. I think you are right about the impedance but the audio controls are on a diffrent circuit. Only the five audio buttons and the 3 bluetooth buttons are seen by the PAC-SWI.
     
    #5 brettray, Nov 1, 2005
  6. DanMan32

    DanMan32 Senior Member

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    The other problem with having an aftermarket HU along with JBL is handling the speakers. How are you going to work both the aftermarket AND the JBL? You can't just feed the aftermarket HU into the JBL amp. Well, if the aftermarket HU has line level outputs, I suppose you could make a switch to change the JBL amp input source. Just remember though, the JBL expects fixed line level, so in this configuration, you would have 2 volume controls.
     
    #6 DanMan32, Nov 2, 2005
  7. tmorrowus

    tmorrowus Member

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    My plan would be to send the JBL head unit signal into the aftermarket HU CD changer input. After all, that is what it is... a super duper changer with bonus of cassette and radio. I would adjust volume with the aftermarket HU (potentially with steering wheel controls using the PAC-SWI).
     
    #7 tmorrowus, Nov 2, 2005
  8. Zappa

    Zappa New Member

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    BrettRay: Would care to share some photos of the installation. I'm gonna replace the HU on my Prius when I get it (2006 EU-version).

    And what I've heard from the dealer it's not the JBL system but the new mp3 HU I'm gettin as standard. BUT it doesn't have DAB radio and the Sony HU I've got at home does and I don't wanna loose that...

    DAB is digital radio via groundbased antenna network abitl ike XM radio.

    Cheers,
    Zappa
     
    #8 Zappa, Nov 4, 2005
  9. brettray

    brettray New Member

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    Zappa:

    I would rather not. :D

    Right now I have a temporary mounting solution; it’s a flat white piece of plastic with a hole cut for the stereo. The white rectangle on the dark gray dash looks really ugly. The pictures would help you decide to not to do what I did. I have plans to make a permanent mount out of wood using a very dark stain. I want to make the piece to connect the round curves of the dash with the flat of the stereo by sanding away everything I don’t need. When I get that done (I plan to start this weekend) I will post pictures. Until then I would be embarrassed to show anything.
     
    #9 brettray, Nov 4, 2005
  10. Zappa

    Zappa New Member

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    LOL, sounds what I've planend todo, but I'm thinking of plastic... People of mp3car.com is really creative of molding up stuff soo in worse case I'll "just" pop by UK and have one of them help me out... LOL

    But I'll wait until you got a clean and nice install untill I starts threating you until you put up some photos...

    But plz do put up a photo before and after the finish up...

    BTW is the stock HU a single din or a 2-din unit??? Or is it one of thoose fancy 1½ -din units???

    /Zappa
     
    #10 Zappa, Nov 8, 2005
  11. jmisola

    jmisola New Member

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    I have just installed my SWI-ALP and the Prius steering wheel controls works well with my Alpine system. All is OK !
    But I have a problem : I have removed the factory HU and now some information on the MFD is not working:
    Upon hitting the power button, the info display comes up on the MFD. It displays NO bars.
    The car works, it drives, the AC works and responds to the temperature up and down buttons.
    Climate button on MFD bezel gives a "Check Air Conditioner Connection" message.
    If I reconnect the 3 connectors of the factory HU, all is working again...
    So it's seem that some informations transit thru the factory HU and the MFD... Removing default HU break an information link..

    Someone can help me ?
    Thanks
     
    #11 jmisola, Nov 24, 2005
  12. akrca4

    akrca4 Junior Member

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    I believe you need to connect a resister between two of the wires. read the instruction in the Metra Kit installation guide.
     
    #12 akrca4, Jan 6, 2006
  13. DanMan32

    DanMan32 Senior Member

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    Yup, a resistor, about 68 ohms to terminate the TX lines.
     
    #13 DanMan32, Jan 9, 2006
  14. akrca4

    akrca4 Junior Member

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    Just wondering, for those with aftermarket HU, what displays on the MFD when you hit the audio button? Any pics appreciated.

    Also, I have '06 package #1 only non-JBL and non-Nav, can I just use the connect the aftermarket HU directly to the stock speaker wires? or I need to run the wires myself. Thanks.
     
    #14 akrca4, Jan 10, 2006
  15. ScubaX

    ScubaX Member

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    You can use the stock wires if you dont mind cutting them. Otherwise get Metra 70-1761 which will connect to your stock wiring and then you splice to the new HU's wires.

    I highly recommend you get new speakers first.

    Also, there will be problems with just removeing the stock HU as the MFD requires the connection. I don't know the specifics but someone went through this recently here on Priuschat. Search for "Metra" and you should be able to find that post.
     
    #15 ScubaX, Jan 10, 2006
  16. Fowler

    Fowler Junior Member

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    This is exactly what I've been looking for, since the stereo in the HK Priuses are rubbish (no CD/MD changer, etc). Now I can dump the stereo and get an awesome Alpine unit which will work with the steering wheel :) Man if only they had one of these that outputs to USB -- removes a huge barrier to the Mac Prius project I was considering.

    BTW, how hard was it to install?
     
    #16 Fowler, Jan 10, 2006
  17. tmorrowus

    tmorrowus Member

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    I don't know about macs, but you can get devices that let PCs be controlled from IR, so you could integrate with the IR output from this thing.
     
    #17 tmorrowus, Jan 10, 2006
  18. Fowler

    Fowler Junior Member

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    Good point! Might be one for the future, but the new iMacs and MacBooks have IR sensors and I assume the new Mac mini will too.
     
    #18 Fowler, Jan 11, 2006
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