Some more additional info (with pictures) for others trying to troubleshoot headlight problems and weird crazy dash indicator light problems. The pictures below were from a '86 FJ60. Other years may be similar.
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This picture below shows the common grounding location on the passenger's side. As noted previously by Pin_Head, it is located behind the kick panel up a bit under the dash on the A-pillar. The passenger's side is very easy to see and access. A few ground wires are crimped together to a single ring terminal and bolted to this location. Check tightness of this bolt. If the connection here is suspect, remove the bolt, clean up the ring terminal and bolt with fine emery and screw back in. A largish gauge white/black grounding wire here leads to another grounding wire junction nearby which joins several small white/black ground wires to it.
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This picture below shows the driver's side common grounding location on the driver's A-pillar. It looks very similar to the passenger's side, with the same type of wire connection. It is kind of hidden and takes a bit of neck craning from down near the floor with a headlamp to see it. The picture below was taken with a small camera placed up next to it. You can not see it this well with just your eyes.
Check the tightness of this bolt. I replaced the original one with a new shiny Toyota bolt. If in doubt of the connection, remove the bolt, clean everything up and reinstall. The original bolt was 1-1/2 turns loose!.
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Picture below shows the passenger's side grounding junction located in the wiring harness. Some of the black harness-wrap protection has been removed in this picture to gain access to the wires. The cabin fan damper can be seen in the background (for reference). The white plug with the green arrow looks like a plug, but it isn't a plug. It is a "common connector" for all the smaller ground wires to join up to one spot. The large white/black wire you can see at the bottom of the group is the one that leads to the A-pillar ground on the passenger' side, as shown above. Carefully examine this grounding junction for frayed wires, poor contacts, melted jacket insulation or any signs of burning.
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This picture below shows the driver's side ground wire junction. The metal cap at the end joins all the black/white ground wires together to a shared junction. A larger gauge white/black wire leads from it up to the driver's side A-pillar common grounding point like the passenger's side does. Examine this plug carefully, but do not disassemble it unless something suspicious is detected.
On to the next post, for more pics...and the discovery of this particular headlight/dash indicator problem.