Short version.
Rip out all your fuses and fit new ones.

Long version.
When I bought my Lbug back in '08 the electrics were pretty sad. Several things were not working due to water leaking thru the bulkhead and dripping onto the fusebox causing corrosion. I gave it a quick swipe and all has seemed ok since.

Until last month when my right hand headlight stopped working. Problem was traced back to the fusebox. All fuses looked ok, and a poke and wriggle did nothing.
When I started removing fuses and having a good look at them the problems started to show.

Half of the fuses had holes and rings burned into the ends, and a couple were burned black on the end.
Not to mention the poor condition of the fuse retainers.

Solution.
Swabbed the fuse holders repeatedly with CLR and wiped them with a damp cloth.
Fitted all new fuses.

Result.
Headlights are nearly twice as bright. Engine idles quieter and smoother. More power, too. Wipers moving a bit quicker.

Best $2.00 and half hour I ever spent on a car!

Hi

I would never have thought to use CLR.. even though I have it.. lol

My fusebox was always getting hot and lights getting dimmer etc..
and I had cleaned the contacts with wire brush and steel wool..
I used to turn the fuses around so they would self clean..

as You have found out, copper gets contaminated over time just from the air, water doesn't help..

I have since replaced the fusebox with a new one with push/pull out fuses.

CLR .. You can dip the ends of your cables,connectors in CLR too..
make them all like new... Great Tip...

cheers

LEE