Interior light to sidelights/parking lights

Hi, DISCLAIMER: The car being modified is a project car not a daily runner so I'd like to do what I want with it before anyway asks the predictable "but why???". This question has been asked before but information on how to do this correctly is thin on the ground. I'm learning about electronics/wiring and have a spare Corsa C wiring loom that was donated to me. Using this loom I have managed to locate the sidelight/parking light relay and correct BROWN / Red wire used to actuate the relay. I then moved over to the working project car, tapped into the Grey wire on the interior light (the 'earthed switch'? - not the constant 12v power) and connected it to the BROWN / Red wire that connects to the sidelight/parking light relay. This simple first step works and the sidelights come on with the interior light but the relay makes a loud buzzing sound when the lights come on and go off, why is this? After consulting the Hanyes manual and wiring diagrams this relay has its own constant power line so too little power seems unlikely meaning it's a case of too much power? Am I approaching this wrong? Should I be using a separate relay and tapping into the wires closer to the lights (after the sidelight relay)? I would of thought using the existing relay for this would work but I am conscious of doing things properly and the loud buzzing from the relay is definitely not healthy. Thanks,

The buzzing of the relay is caused from the fading /dimming of the dome light. The simplest method would use a transistor (pnp) to trigger a relay, which would trigger your parking light relay. If you don't want to use another relay, you need 2 transistors (1 pnp/1 npn) and a resistor at the very least. Diodes are always handy too. It's been quite a while for me, so I don't remember off the top of my head exactly what part numbers/values/components you'll need, but it should be a good learning experience if you are getting into electronics. Search for some basic transistor tutorials and go from there. There are many tutorials, but look for the one's that don't assume you were born with a doctorate in electrical engineering. That's what I did, and I learned just enough to do what I needed to do. You are correct the relay chattering is not good.My ex once told me I have a perfect face for radio.