How do you troubleshoot a headlight problem?

Answer 1

Check wiring on back of lights, exchange globes with someone who has same car, check fuses(they should be labelled), check voltage after the headlight switch with inexpensive multimeter. Use voltage tester with sharp probe to test voltages on the wires to see if power is getting to the lights and if not follow the wire back until you find voltage.

i am getting a power but one of the lights is weak other is strong!!

If that's the case, either something is going to ground on the weak side or the ground itself is weak. Check the bulb plug after unplugging it, looking for dirt, corrosion or damage. If dirty or corroded, it can be cleaned. After cleaned, apply some dielectric grease to the plug before reintalling.

Always remember to never touch the bulb glass when changing bulbs! These bulbs heat up very rapidly. Skin or other oils can cause just enough insulation to result in uneven heating which can shatter the bulb.