By on May 18, 2015

occam's razor. Shutterstock user OpturaDesign

Robin writes:

Hi Sajeev,

It’s me again, steady reader, random poster/questioner, with another D21 question. My good old ’94 Nissan D21 is soldiering on, 213,000 and steady on. Of course I don’t ever thrash it which I’m sure makes a difference.

But to get to the point: the other day I went out to go to work and presto! No low beams. High beams, check. All signals, markers and brake lights, check. Just no low beams.

Forum surfing ensued, all seemed to point to the switch stalk. I checked fuses. No headlamp fuse? WTF!


What the… (photo courtesy: OP)

I’m hoping against hope that it’s something simple and stupid that I’ve overlooked in my attempts to shoot the trouble. And that another Piston Slap reader has a tip.

Because Piston Slap is only run twice a week, Robin beats us to the punch:

Hi Sajeev,

I emailed you not too long ago about my D21’s low beams going out all at one time. Replaced the switch stalk (a common culprit per several forum threads I browsed), scratched my head furiously over the fuse panel, girded my loins for the big $ hit of having someone with a clue troubleshoot the electrics. In the meanwhile, I drove around with my high beams on, undoubtedly pissing off my fellow North Texans.

So this morning I decided to just replace both sealed beams. At worst I’d still be in the same boat but new bulbs. Voila! It was the ultra-rare concurrent low beams burnout phenomenon.

Old Bill from Occam really knew his stuff.

Sajeev answers:

I’m glad to hear you fixed it. Perhaps you also needed that new headlight switch, as it sounds like a multifunctioning switch which are known to misbehave in the oddest ways after 10+ years. Anyone with even a passing interest in Nissan Hardbodies should download this PDF. Yes, it’s for a 1990, but it’s a start.

I looked at page EL-41 and saw nothing fishy about Hardbody headlights: fuses, connectors, grounds, etc as expected. I am stumped as to why your 1994 fuse box doesn’t list a fuse a la the 1990 shop manual. While I think Occam’s Razor applies to the 15A fuses (if you have them!), having both headlights blow out simultaneously is odd but the obvious problem after that. Why?

Bonus! A Piston Slap Nugget of Wisdom: 

Because headlights are a wear item. I’ve said this multiple times before, if your halogen bulbs are 5+ years old and the filament’s shiny finish isn’t chrome-like (it’s tungsten, but you catch my drift) in perfection, they probably need replacement. Hell, I’ve seen a certified pre-owned, two-year-old used car (presumably with thousands of night miles under its belt) need new bulbs so the new owner can see safely at night.

[Main image: Shutterstock user OpturaDesign]

Send your queries to [email protected]com. Spare no details and ask for a speedy resolution if you’re in a hurry…but be realistic, and use your make/model specific forums instead of TTAC for more timely advice.

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19 Comments on “Piston Slap: Occam’s Razor Cuts Hardbody Headlight Headaches?...”

  • avatar

    The plaid sweater vest is smashing.

  • avatar

    I’d just run a new relay for the low beams, triggered off the parking lights, right at the lights. Same as if you were adding fog lights. Cheap and easy. One new lead from the battery, direct.

    1st click of the factory switch and the parking lights and low beams come on together. I’ve done the fix for Fords, GM mostly, and I consider it a true fix, rather than replacing the crazy expensive stalk that’ll eventually fail again.

    • 0 avatar

      Did you bother to read the whole post? It was burned out low beams on the bulbs.

      Keep that Hardbody going! Without rust to worry about (their mortal enemy) it shouldn’t be too hard, D21s are absolute tanks.

      • 0 avatar

        Yeah but it still could be the switch/wiring for the next truck. Both headlights don’t usually go out simultaneously. You start with a test light.

  • avatar

    Another halogen lightbulb tip: when you buy a replacement bulb, look for where it was manufactured.

    My CR-V seemed to need replacements on a regular basis. Looking for a pattern, I started writing down when I replaced bulbs, and which one (I think both high- and low-beam are H1 bulbs).

    I concluded that if I bought an Osram Sylvania bulb made in China I might expect a one year life, but if I got a bulb from the same manufacturer but made in Germany I did not see early-life failure. Now I spend a couple of bucks more per bulb, but it’s worth it.

    • 0 avatar

      There’s definitely a thing with pattern failures in aftermarket components of dubious quality. We all know the story “man that thing was a piece of crap, kept eating power steering pumps!” Chances are, the shop the person took the car to kept throwing the same junk parts store reman pumps on there to replace the one the failed previously. Headlight bulbs are notorious examples, as you stated. As far as I can tell the bulbs in my 1996 4Runner are the original ones, this article definitely is prompting me to replace them with fresher bulbs. I’m tempted to avoid the headaches and go straight to the OEM Toyota part.

  • avatar

    Glad you fixed it.

    If my memory is correct (thinking into the wayback machine here) there were either fuses or fusible links for the headlights right on the positive battery lead at the battery.

  • avatar

    It just shows you, always start with the bulbs, then move on to more complicated issues.

  • avatar

    A $5 electrical test probe is worth its weight in gold.

  • avatar

    After a lengthy (and slow) towing run across America in the summer of 2013 I had no taillights (but headlights – turn signals – etc.) on my F150. It wasn’t even a blown fuse (my first suspicion) but the damn thing had wiggled loose just enough to confuse things.

    • 0 avatar

      My old Toyota pickup once had a problem where it would randomly just die; engine would stop running, randomly – and start up again *most times* if you turned the key, and always did eventually.

      So I took it to the shop, and they spent a few days looking at it and scratching their head, and replacing the FI pump relay and other stuff.

      Before they figured out it was a loose wire behind the fusebox that was cutting power to the FI pump.

  • avatar

    This happened to my buddy’s 2008 Frontier recently. It’s a U.S. import (to Canada) so he figured the aftermarket DRL module might be the culprit. He didn’t want to deal with it so he took it into the shop. It just needed two new bulbs.

    I had a strange one with a girlfriend’s ’94 Tempo way back when. Both headlights would briefly cut out whenever you hit a significant bump. I figured a ground must be loose, but in the end it was the bulbs. Both filaments were broken but still making contact while at rest. Flip the bulbs over and the filaments would just dangle.

  • avatar

    I watched my mechanic trying to figure out a double low beam failure on his brother’s two year old Prius. It was a two, so it had traditional bulbs not the fancy HID. He was going over and over the problem in his head, searching for a root cause. Yep, both bulbs went at the same time.

    In my various classic Saab 900/9000/9-5 vehicles, it was more often the solid state relay in the orange box that would rattle one of the solder traces apart. The headlights would stop working, or brights would stop, or some combination of the two. I think that about 5% of the time it was the bulb. I carried at least one spare relay in lieu of carrying a soldering iron…

  • avatar

    Seems that more than most subsystems, electrical subsystems often fail in specific ways depending on the underlying vehicle. And one you figure out what that is, and begin carrying a spare, the electrics on the vehicle become manageable. Fail to find that weak spot, or to plan for it, and you will find yourself complaining about the lousy electrical system on your car.

    Old Norton motorcycles used a Zener diode under the rider’s seat as a rectifier to get DC current. First time a rider would hit a bump fast enough and/or hard enough to bottom out the seat, the Zener diode would get hit hard enough to crack it, rendering the Norton inoperable.

    After an initial occurrence, a more experience rider would tip off a new Norton owner to carry a spare Zener diode (about a $5 part), and how to replace it.

    I personally went through about a half dozen, but after the first, was never down for more than five or ten minutes, nost of that to rest a bit while making the repair.

    But even years later I would read or hear about Norton owners complaining about the unreliable Lucas “Prince of Darkness” electrics on the bike. Yet except for a burned out bulb once or twice, I never experienced any other electrical problems with the bike.

    And I too have verified that manufacturer and/or country of origin often seem to have a strong correlation with longevity.

    On an Isuzu Trooper, repeated electrical fuel pump failures at short intervals, days, weeks, at most a couple of months, ceased when a wise mechanic suggested replacing both the pump and its housing, through which the pump was grounded. A definite ground connection through a ground wire to a ground post on the frame would have been a much better idea, but since Isuzu didn’t do that, at least making sure its housing grounded properly changed the Trooper from a maintenance nightmare back to a workhorse again.

    Find the weak link, and the rest of the chain is often reliable. I’m sure that there must be counter-examples, but mostly I have just seen the pattern “weak link in overall OK subsystem.”

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