Thread: Help with hooking up steering wheel controls

That doesn't look like amps. Don't switch to amps until you understand it. It's basically like replacing a wire with a meter to measure current. Over 10 amps will blow the meter or it's fuse if it has one.

First you should figure out where the power is coming from. Disconnect the radio and see if that does it. With a gamepad/joystick, you'll need to drop the volts to 2.5 or with fusion brain, 5.0 which is much easier, so the unregulated 14+ is a little harder to work with. If you can remove that and replace it with the 5.0 from the gamepad it will be as easy as adding a couple resistors. Otherwise it's less safe. God_of_CPU uses a diode to block it and reverse the current but I think you need both wires to work with.

Yes, that would be milliamps. Don't use it. Just use the 20V setting. Do you have the black lead of the meter connected to the car's ground? Do you have any resistors laying around?

Yep. FB would be easier too.

Just putting a 470 ohm between the two inputs on the meter will allow you to see volts when pressing the buttons. Using the divider will drop the volts to a safe range for the FB or gamepad, but the gamepad will need an input of 2.5v when no buttons are pressed because it will calibrate a center position. For the FB it would only be like
SWC--/\/\/\--<input>--/\/\/\--Gnd

ok, to simplify things for you a bit, what you need to do is disconnect the SWC from the car completely. It is a two wire system and is nothing more than a bunch of resistors in parallel with a momentary touch button breaking the lines between all but one resistor. when no buttons are pressed, you are going directly through one resistor. When you press a single button, you are allowing the current to go through two resistors in parallel. To calculate the resistance of each resistor in the circuit, you first disconnect the leads. Next make certain that your voltmeter has a good fresh battery and set the meter to reading resistance (Ohms). Typically you will be in the 200 to 2000 range, so start small and go up on the voltmeters dial as necessary. Now hook the red lead to one wire and the black lead to the other of the SWC. Now you are measuring the resistance of the "always on" resistor, write that value down, you'll need it soon. Next, you need to press each button and jot down the value for that button on a seperate sheet of paper because it is NOT the value of the resistor under the button you are pressing... To get the value of the resistor you are adding to the circuit (in parallel with the Always On resistor), you use a derivation of Ohm's Law, 1/Rtotal = 1/Ralwayson + 1/Rbutton. Now you should be able to do anything you want with the circuit, because you know what the resistances are, and can calculate what values you will get out given a specific voltage, again using Ohm's Law. If you would like to cheat and use a calculator, go to the PAC website, they manufacture SWC to HU controllers and have a nifty calculator on their webpage, along with diagrams and such. I'm in the process of replicating the factory SWC for my Subary Outback using the blank plastic piece where the buttons should be.