I've got the Hella 7" lights and sometimes the drivers side headlight will not light. If I tap the glass it then lights. I've put some lithium grease on the plug and made sure the contacts are OK but the light still only comes on after a little tap. Does the surround of the headlight act as an earth or something ? (1/00)
AFAIK the 3 pins on the bulb are for dipped +, main + and ground. Therefore the lamp casing does not act as a earth. Have you tried replacing the bulb, your problem may be caused by a problem with the bulb ? Does the lamp only work when tapped on both main and dipped beam ? (1/00)
You need to work the connectors/spades on the lamp terminals... take them on and off about 10 times to break the oxidisation layer; just grease is not enough .. and silicon grease is the best! (1/00)
Anyone know what the extra little copper colored connector is for on the back of the hella??? The stock connector fits the top three connectors, but other one is below these, is it for "really" dim? (or am I?) (1/00)
This is for a side light connection. There is a fitting for a bulb here as well AFAIK cant remember the exact details but I think this is correct. Not much use for the '5 though (I dont like the pop ups on anything but headlamp). (1/00)

In my experience (from several years of Metro ownership :-( ) when you have to tap a light to get it to come on, the filament may be broken: the filament breaks - hence no light you tap the light- the jolt makes the filament hit the other conductor post in the bulb and the filament/post 'weld' together temporarily. several days later it happens again. How many times you need to do this depends on the bulb. Eventually the filament goes a knacker altogether and a good whack won't do anything.

this incidentally happened over christmas when a sidelight bulb on the'lego racer' finally went. I changed both bulbs (cause they both looked in a poor state), since also in my experience driving with one light (headlamps generally) weakens the operational one so when you get the duff one replaced, the other one goes, so you weaken the 'new' one. I went through about 5 bulbs in a fortnight on my old metro because of this. If a headlight goes I change both always. (1/00)

Yup I have seen this before to, I also change the pair of bulbs if/when one bulb blows. (1/00)