First gather together what you’ll need. First and foremost you’ll need a nice new H1 bulb.
Additionally (and optionally) you might find the following handy:
Torch
Wide blade screwdriver
Inspection mirror
Small hands
Patience
What follows covers the driver’s side, but the other side is the same –give or take the washer bottle.
Pop the bonnet and you’ll soon see there’s not a lot of room to work. The trick here is to remove the top part of the washer bottle. Release the washer bottle filler neck from its bracket by sliding it diagonally forwards toward the centre of the car (a wide blade screw driver may help). Lift the filler neck, cap and dip stick completely out of the way.
You now have access to the grey cap on the back of the headlight. This is more of a bayonet than a screw fitting. Rotate the cap clockwise (viewed from the front) noting the movement of the lug on the cap within the recess on the headlamp body. Withdraw the cap from the headlamp.
Trying to get the cap out of the engine bay (past the VSA and air con tubing) is like a Chinese puzzle. So don’t bother. It’ll be quite safe if left beneath the headlight. Edit: It’s worth removing the cap entirely just once and applying the thinnest smear of silicon grease to both sides of the rubber seal. It’ll make fitting and removing much easier next time round.
The next part is done entirely blind by feel alone. Reach into the back of the headlight and locate spade terminal on the back of the bulb (it has a silicon boot on it) and pull it off. Next feel for the curled end of the bulb retaining spring. Push this forward and then left to disengage the clip from the retainer. The old bulb will more or less fall into your palm.
Refitting the new bulb isn’t quite as straight forward as it seems.
The hole in the headlight is a vertical slot and only just wider than the bulb itself. The flat part of the bulb stem has to be aligned vertically, and crucially the right way up. Once installed the bulb cannot be rotated, so it has to be right first time.
As you’re working only with your finger tips and can’t really see, it’s surprisingly easy to fit the bulb upside down, fit the retaining clip, connector, back cap and think you’re done –only to find the beam pattern is all wrong the first time it goes dark
The correct alignment is with the cut corner pointing diagonally up towards the negative wire of the headlight. As mentioned above it will (kind of) fit the other way, and it doesn’t look or feel particularly wrong when you’re doing it.
When handling the bulb take care to avoid touching the glass envelope. The glass runs at around 200oC and contains very high pressure gas. Skin oil on the glass can cause it to rupture explosively, as can scratches on the glass surface, so take care when passing it through the slot in the (die cast metal) headlight ***embly.
With the bulb in the right orientation re-fit the spring clip. Easier said than done whilst trying to prevent the bulb falling out of the housing. Once done, put the spade connector back on the back of the bulb. It’s worth switching on the lights at this stage, just to check it’s a worker.
The grey cap can now be re-fitted. Note this will only fit one way up. Rotate the cap before fitting so the lug is upper-most and locate it in the recess on the headlamp body, then rotate anti-clock (viewed from the front) to tighten.
Slot the washer bottle filler back in its keyway and you’re done.