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1984 Mitsubishi Colt with left headlight out. I tried replacing it but the unit is sealed and it's going to be a mess around if I can even find another replacement light, let alone fix the current one.

So my problem and symptoms:

  • High beams work perfectly. Both holding on and switching on works a treat.
  • High beam lights go through same bulb (or unit), parkers are different but work too.
  • Sometimes when I turn on the lights (and dash lights/parkers), the lights for my cluster and inside car don't turn on, so I have to turn off and back on again. In this time, the headlights work fine (except of course the broken left headlight)
  • Fuses all look perfect. Could switching them be any use?

Does a car like this, old and mechanical even have an extra place I can check for faults for one headlight? Could it be something in wiring rather than a burnt out bulb?

  • Welcome to Motor Vehicle Maintenance & Repair! It appears the two headlights are different, left to right, is that correct? Even so, you may be able to take the known good headlight from the other side and test it in the bad headlight spot by just plugging it into it. This would tell you whether it's the bulb or the wiring and give you a direction to go with you troubleshooting. – Pᴀᴜʟsᴛᴇʀ2 Nov 2 '17 at 3:12
  • They're different, but both stock. THat's a good idea and I wanted to try that last time I tested, but it takes a lot out of you getting to these headlights in this car. Is it even possible for a bulb to be "burnt" but still work on high-beam? – insidesin Nov 2 '17 at 4:01
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    Absolutely, because in order to have a low beam and a high beam, there has to be two separate filaments. One can be shot while the other still working fine. – Pᴀᴜʟsᴛᴇʀ2 Nov 2 '17 at 4:03
  • AH, that makes me more sad :P But your idea is great. I'll definitely have to spend a few hours testing and looking again. Not sure where I'm going to get a 30+ year old headlight that still works... – insidesin Nov 2 '17 at 4:11
  • What I'm seeing online is this is a composite unit and not a sealed unit. I mean, you're the one who's there looking at it and it's your vehicle, but I've seen headlights which have a glass lens, but still have a plug in bulb. What I'm seeing is it being an H4 bulb. Would be a heck of a lot better getting an H4 rather than a complete unit, that's for sure! – Pᴀᴜʟsᴛᴇʀ2 Nov 2 '17 at 4:37
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The fact that you get intermittent fails in unrelated systems (the cluster/interior lights) makes it sound like some kind of pesky electrical fault. I don't know the vehicle, but it likely has a large wiring harness under the steering wheel or near there for all the headlight/turn signal switches etc. Get a good wiring diagram, unplug the harness, then do continuity & voltage tests on all the major connections points.

I had a similar, infuriating issue where the headlights in my vehicle would just go out randomly. Later on they would work again but they were very unreliable. I tried replacing the master switch and a few other things. Finally just had to dig in and test every connection in that harness.

Guess what I found? One of the +12v leads to the light switch had come unplugged a bit, which caused excess heat that further degraded the harness connection, and it happened to be the one that fed the headlights. It was bad enough I had to pull the wires out and splice the connection around the harness, but the headlights worked like a charm after that.

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