# Thread: Help me separate my steering wheel controls from my head unit for use with brain

1. ## Help me separate my steering wheel controls from my head unit for use with brain

I was able to find a wiring diagram of my steering wheel controls and I'm hoping you guys can help me separate my steering wheel controls from my head unit. Right now when I separate wire #14 from C3 I don't get any resistance. This is probably something simple for someone who knows what they're looking at .

I have my brain all set up to do commands based on my resistances... The problem is those commands also issue the commands on the head unit doh.

2. put a probe from a voltmeter set to volts DC on wire 14 removed from the HU, and the other probe on a ground point, and hit buttons. what happens?

3. Here is a simplified version of the schematic you supplied so you can easilly understand whats going on.

Each button simply shorts out resistors in the voltage divider to vary the output voltage, which then can be interpreted by the Fusion Brain.

So all you need to do is connect a 560 ohm resistor between pin 14 and GND, and connect the Fusion Brain or multimeter across the resistor. Now you dont need your radio anymore!

If you still want to use your radio then just simply connect the brain across pin 14 and GND, and leave out the 560 ohm resistor.
**NOTE if you get a voltage greater than about 4v with the "VOL +" button pressed with the radio connected, then an additional voltage divider is required to protect the brain!!

The 560 ohm simply replaces the resistor that is actually inside the radio.

* 560 ohms was calculated to give a maximum of 5v into the fusion brain when the supply voltage is at 16 and the "VOL +" button is pressed (in case of glitches n stuff)

4. Wow that's perfect. Thank you both very much.

5. Civic_Modz, great image. That is exactly what you need. But remember as he said, measure that voltage when you are pressing buttons. If any of them are greater than 5v at any time, you will need a second divider, which is just 2 more resistors.

6. Yeah. I have this all working, I just need to separate it from the head unit now. One other thing, did you make any progress with the chipsets that can't be used with the brain? I still can't use my carputer with the brain .

7. Originally Posted by 2k1Toaster
Civic_Modz, great image. That is exactly what you need. But remember as he said, measure that voltage when you are pressing buttons. If any of them are greater than 5v at any time, you will need a second divider, which is just 2 more resistors.
really he should just increase the value of the 560ohm resistor until it drops under 4vdc with the car running

8. The closest I could find was a 680 ohm resister. I tested it with the volt meter and it shows my highest voltage as 4.20. My head unit is GONE! Finally! You guys are great.

Is 4.2 low enough or should I put a higher resister in? I thought the brain was ok up to 5v?

9. Originally Posted by scotty562
The closest I could find was a 680 ohm resister. I tested it with the volt meter and it shows my highest voltage as 4.20. My head unit is GONE! Finally! You guys are great.

Is 4.2 low enough or should I put a higher resister in? I thought the brain was ok up to 5v?
Yup anything less than 5v is ok. You're fine.

10. I agree with 2K1.
As long as when the "vol +" button is pressed and you can read less than 5v (While the car is running!) you should be ok.

Just be aware that the voltage you read might be slightly different when the car is on as opposed when it is off. If you read 4.2v when the car is off and running, you have nothing to worry (Would be internally regulated)

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