XJ6 & XJ12 Series I, II & III 1968-1992

Headlights - curious behavior

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Old 01-15-2020, 11:05 AM
worzella's Avatar
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Default Headlights - curious behavior

86 SIII

I need to look at wiring diagrams and poke about with my voltmeter a bit more, but I have a question. My left side low beam went out a couple days ago and I read all of the suggestions about cleaning fuses first before replacing bulb. I could not do much in the dark last night, but noticed an odd behavior.

With high beams off. the right low beam works, but the left low beam is out. However, when I switched on high beams I was quite surprised to see all four lights working... the two highs, the working right low beam AND the "non-working" left low beam.

Good thing is that this told me the bulb is OK. So to me it would appear that when running high beams, the current for ALL four bulbs is flowing through the 35A L/R high beam fuses. And it seems that when just low beams are on, the current flows through the L/R 20A low beam fuses. Is that possible ???

I will swap the two 20A low beam fuses to see if that swaps which low beam is not working, so it might just be a simple fuse issue.

Thanks - Randy
 
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Old 01-15-2020, 11:15 AM
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Originally Posted by worzella

With high beams off. the right low beam works, but the left low beam is out. However, when I switched on high beams I was quite surprised to see all four lights working... the two highs, the working right low beam AND the "non-working" left low beam.
Remember that the outboard lamps have two elements, hi and lo.

I suspect what you're seeing is that the "hi beam" element of the left outboard lamp is working but the "low beam" element is not.

I suspect your LH outboard bulb needs replacing

Cleaning fuses and connections at the headlight fuse box is never a bad idea tho !

Cheers
DD





 
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Old 01-15-2020, 11:20 AM
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Awesome Doug.. I did not realize that and I will remember it for next time. I did buy a bulb so I will change it out and see.

Randy

 
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