Daytime Running Lights
Translation:
Do not use any supplies of the car to directly power any addition. Use it only to trigger a relay.
The currents switched at the column stalk are very low, possibly only 5v anyway. I think the column switch is just a series of earths, via different resistances. The ECU reads the voltage drop and uses this as a signal to operate whatever is requested. This can occasionally bring strange results.
(Vauxhall on the Mk5 Astra, 2004 on, had issues where the horn switch raised the radio volume instead.) So splicing into anything from the column switch will bring disappointment.
With CanBUS, the car functions are triggered and monitored by the ECU using small wires and small currents. These are not power feeds. To find a power feed, you need to get close to the fed unit, in your case the headlamps, so you need to splice into a wire close to the headlamp, where you know it is a 12v supply. But do not use this as a feed to your additional lamps. The ECU will monitor the current along this wire, and throw up a fault warning if it is wrong. Instead use this to trigger a relay, so only a small added current, which should be acceptable to the ECU. Then the relay will take battery voltage to the additional unit you are fitting. Ensure your new feed is fused.
