The brief
Mr Jimmy's Golf had a headlight issue, the kind of small fault that's easy to put off but is the sort of thing that fails a check and leaves you driving half-lit at night. He brought it in. A headlight that's dim or out usually comes down to one of a few things: the bulb itself blown, the connector behind it corroded, or a wiring fault feeding it. The bulb is a consumable that dies on its own schedule, and the connector behind the lamp sits in a warm, damp spot in the engine bay where the contacts corrode over the years, which makes a poor connection that dims the light or kills it. A blown bulb doesn't come back and a corroded connector only gets worse, so both needed sorting.
The diagnosis
A check of the headlight found a blown bulb and the connector behind it corroded, the contacts dull and making a poor connection, which is the dim-then-dead behaviour. The headlight unit itself, the switch and the wiring back to it were fine. That's a bulb replacement plus a connector clean and repair, not just a bulb that would soon flicker again on a bad contact.
The work
The blown headlight bulb was replaced with a new bulb of the correct type, handled clean so no oil on the glass, and the corroded connector cleaned up and repaired so the contacts bite properly again. With the lamp working, the beam aim was checked and set so it lights the road without dazzling oncoming traffic. The other side's bulb and connector got a look while we were in there. A check at dusk confirmed both headlights bright, steady, and aimed right.
The outcome
Both headlights bright and steady, no flicker, the beam aimed properly, and the connector solid. The Golf went home with the lights sorted. A blown bulb on a corroded connector is the sort of thing that comes straight back if you only swap the bulb, so cleaning the connector and checking the aim made it a proper fix.