Headlight won't open

Do NOT remove the assembly (bucket) unless you absolutely must. First disconnect the cable at both ends (loosen clamp, wiggle wiggle, then pull. Now you can tell which of the three components: headlight mechanism, cable, or crank is tight.

I have one headlight that opens smoothly but the left one won't budge. I'm assuming I remove the assembly from inside the fender well and fix it there. Is this usually (if there is a "usually") the mechanism or the cable?