I got this done, finally. I'll prefix this by saying that I am not going to sell these. There's too much that can go wrong and the potential liability is not something I want to deal with. Plus, I spent about 4 hours on this project yesterday and that's just not effective from a cost perspective.
Anyway, here is a video of the switch working:
Here is the wiring "diagram", if you can call it that. I am not an electrical engineer so I don't have electrical drafting skills
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I used the following items, some of which I had on hand, some of which I bought specifically for this project:
The general fabrication procedure I followed was this:
- Drilled a hole in the side of the box to match the requirement for the switch
- Labeled the switch wires so I could keep track of which was what
- Install the switch into the hole and tighten the retainer nut
- Drill small holes in the side of the box to pass wires in and out of the box
- Plan where add quick disconnect terminals - this makes stringing wires through tight spaces easier.
- Strip end of the wires as necessary; pre-tin wires and the terminals on the resistor. Plan where your shrink tube will go and pre-stage the tubing on the wire as appropriate - you can't retroactively do that after soldering.
- Pass the wires through their respective holes, create the "mute/off" circuit first by soldering the supply hot to the common switch wire, then the "off" switch wire to one side of the resistor, then the other side of the resistor to the Negative supply wire. Use the multimeter to verify continuity and that there is matching resistance. Use heat to shrink the tubing over the soldered wire to insulate it.
- Create the 'on" circuit by soldering the "on" switch wire to the "hot" wire that will go to the speaker, then splice the speaker negative into the negative wire that goes to the car harness. I used a quick/vampire splice, but you could use any method you like, just make sure you splice into a point that does not include the resistor in the circuit. Use the multimeter to verify continuity and that resistance is close to nil. Heat shrink your tubing over solder joints.
- For the car side connector, assemble the connector housing and terminal repair kits. Strip a small portion of the wires, then crimp quick disconnect terminals onto the wire ends to connect the hot/negative "supply" wires to the wires going "to" the box. I made sure to alternate the male/female terminals so that you can't swap polarity by mistake. Now is a good time to make sure you have continuity between the terminals in both "on" and "off" switch positions. "On" should have continuity with close to 0 resistance, "off" should have continuity but with 8-9 ohms of resistance.
- For the speaker side connector (Corsa Technic kit), slide the included gaskets over a new length of wire not attached to anything, and strip a small amount of insulation. Slide one of the terminals over the exposed wire and crimp it so that the lower prongs secure the gasket/wire insulation while the upper prongs secure the exposed wire. Do this for both terminals. Determine which side is to be the hot vs the negative, and slide the terminals into the connector, then press the white tab in to secure the terminals in place. Crimp quick disconnect terminals on the opposite wire end in the same way as above, and complete the wiring by attaching them to the wires on the wire pair coming "from" the box.
- Use silicone sealant to close off any gaps around the holes drilled for the wires to pass. For good measure, apply on the box interior and exterior. Wait for the silicone to cure before proceeding.
- Put the top on the enclosure and screw together securely.
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General install process
- Open the hood and remove the plastic trim piece
- Disconnect the car side of the connector from the speaker/remove existing by-pass if applicable
- Identify where you want to mount the box and how you want to run the wires to their respective connecting points. (Ideally you should do this before you start fabrication so you know how long your wires need to be before you start)
- Run your wires as desired, taking advantage of the quick disconnects to snake wires through tight spaces if required, and the connect everything up.
- Test - Get someone's help to stay in the cab with the vehicle in reverse so they can hold the brake. Validate there are no PVNS errors on the MID. Toggle the switch between on/off positions and make sure that you hear the reverse noise in the on position and blessed silence in the off position. Park and turn the vehicle off. Toggle the switch to off/mute. Turn the vehicle back on and make sure there are still no errors showing on the MID. If at any point you get a MID error or the speaker doesn't sing when it should, turn the vehicle off and check your wiring.
- If all is well, wrap electrical tape around the quick disconnect terminals to prevent shorts, finalize your wire routing, reinstall the plastic trim, and mount the box as desired.
Here's my final install:
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