EWIS anyone ?

Nice and shiny, moparmat!

And yes, BillGrissom, I was referring to the alumiprep. Chemical regulations are quite different btw EU and US.

On a general note, what moparmat is doing here is probably something everyone should be doing. Things can deteriorate severely over the years depending on what climate you live in.

On my old Audi, I got a little over 9 Volts over the bulb in my headlights after 15 years of service, always parked outdoors. I could barely see the road. With the complexity of a modern car, I decided to add a secondary relay in stead and draw a new wire straight from the battery via a fuse. That and cleaning the lenses made the lights shine like new again. Rear lights are still dim, though... Lazy me. :D

Worst case, poor connections can melt connectors or even cause a fire with older, non-UL94-rated plastics. UL94 is a certification that plastics self-extinguish rather than turn your car into a fireball.