What a great mod!
I can confirm that our 2006 needed to have the black & yellow wires reversed in accordance with your instructions.
Here's a dumb question: is there really a need for those 2 diodes given that the map LEDs are diodes themselves? Or is that more a safety precaution against the possibility of someone replacing the LEDs with incandescent bulbs?
Thanks for the nice words and for the info about the 2006. It's certainly starting to look as if the entire SG line was wired that way. Now I wonder about the SFs and SHs.
Funny you should ask about the diodes, as I'm working on the final draft of a tutorial on diodes like the ones I just did on
relays and
multimeters. Here's an excerpt:
The object of the mod is to turn both map lights on when the dome light comes on, but to keep the map lights themselves working the same way they used to work, with each map light’s switch controlling only that light.
Well, you could get the map lights to come on with the dome light simply by wiring all three in parallel. That would satisfy the first objective of the mod, but it would certainly fail at the second. So we inject a couple of diodes into the circuit to isolate the dome light from the effects of the map lights and the map lights from each other. Here’s how it works.
When the dome light is grounded, either by its switch or by the ‘integrated module’ that connects to the door switches, this also creates a path to ground for each of the map lights through their respective diodes. Electricity flows in the direction of the arrowheads, and all three lights come on. But when either of the map lights is grounded through its own switch, electricity from the dome light or the other map light can’t get to that ground because it’s blocked by the turned-on map light’s diode.
As for the LEDs, yes they're diodes, but the electricity from the other lights would never get that far up in the circuit even without the diodes, so they don't feature in what's going on. It would stop at the grounded switch. In general, it's not good to rely on LEDs to act as diodes unless you're aware of and respectful of their maximum reverse voltage rating, and that's an unknown in this situation. I doubt that you'd ever see that spec published for an array, just for individual LEDs. And some LED arrays are configured so that they work in either direction anyway—like the 14-LED units I've been using in other mods.
Too gutsy to take a chance, especially when you can get diodes for a nickel apiece or less.
And one aspect that I didn't think of when putting the tutorial together, though I did note it in the description of the mod here: without the diodes you might create a short across the dome light controller if you opened the doors while one of the map lights was turned on with its own switch. The controller would try to go through its dimming procedure, but all the time its output would be grounded. Results unknown. $$$ perhaps?
Diodes isolate!
