Retrofit Auto Lights

[TrophyJem]

Hi All,

First time post, so please be gentle with me.

I recently purchased a Zafira Tourer (I believe that the tourer is based on the Astra J hence the post here) and I wish to retrofit auto lights. 
Auto lights will be really handy for me as I do a lot of driving in France and Spain, and I'm forever forgetting to turn off my lights when I exit tunnels and underground car parks. 

As I see it i have two possible options.

Option - 1
Buy a headlight switch that has the auto lights position.
Buy the correct sensor
Wire it up (assuming I can find a wiring diagram)
Get it programmed with Tech2

Option - 2
Make my own circuit that that switches a relay when the ambient light falls below a certain level. (I'm an electronics engineer so the circuit is pretty simple).
Wire the relay across the light switch so that the off position of the light switch effectively works as the auto lights position
Have the circuit so it only operates if the ignition is on (don't want the lights coming on with the ignition off).
This assumes that the light switch is a simple dumb switch and doesn't switch a can bus.

Any thoughts / ideas gratefully received.

[Rusty2009]

Ok first off Tech2 won't work on the Zaffy Tourer (or is very limited).

For Auto lights you would need the following

light switch
Light and rain sensor
New windscreen
a loom or 2 and any extra wiring.
bracket and cover trim.

Also VCI request to access the software (if GM will provide a VCI of course)

Best way to do it is buy a switch and sensor get it all plugged in then get a VCI requested and if successful then buy the new windscreen.

[TrophyJem]

Mmm in that case I'm thinking my own circuit will be a better plan. Don't fancy the expense of a new windsceen.

Does anybody know if the light switch is just a dumb switch, or if it switches the canbus directly?

[Rusty2009]

It sends the signal to the BCM then the BCM send the correct signal to each item, so it's all done via the canbus


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[TrophyJem]

Any idea where I could obtain a wiring diagram for the light switch?

[Rusty2009]

https://www.vxoc.org.uk/Images/rusty/S30...Switch.pdf