Ohhh it works with the seat heater switch! No problems there.
Here is a teaser of the modded switch (and my homemade harness)
PLEASE NOTE: This is a homemade harness and is nowhere NEAR as elegant as the harness that will be built by bdl99! The automotive connectors I used were to ensure I could plug and play the entire harness back to factory if I wanted to without unsoldering any connections. All connections that I made that were permanent were soldered and shrink wrapped.
Switch with top unmasked
Switch after flat black paint
AV Head end of harness. Notice diode in green wire taking power from ignition. Red wire taps back into the reverse signal line for 12v feed. Orange and brown wires break VSS at the switch.
Switch end of harness minus switch and switch ground wire. Relay wired as:
mmmi87
mmm87a
86
mmmmm85
mmm30
87 is open and shielded. 87a is brown wire, 30 is orange (always on unless switch activated). 85 is ground and 86 is feed from switch to activate relay. Notice red wire feeding reverse signal has a diode in series to protect the circuit from back feeding.
And a shot of the finished switch in place
and with the lights on (backup camera mode)