Piston Slap: Occam's Razor Cuts Hardbody Headlight Headaches?

Sajeev Mehta
by Sajeev Mehta

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 sajeev@thetruthaboutcars.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.

Sajeev Mehta
Sajeev Mehta

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  • Revjasper Revjasper on May 19, 2015

    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...

  • VolandoBajo VolandoBajo on May 22, 2015

    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."

  • VoGhost It's funny, until CDK raises their prices to cover the cost. And then the stealerships do even more stealing because they're certainly not taking the hit - why do you think they make all those political donations? So who pays in the end?
  • VoGhost I was talking today to a guy who pulled up in an '86 Camry. Said it ran like a top, got 30 mpg, the AC was ice cold and everywhere he goes, people ask to buy it. He seemed happy.
  • VoGhost TL:DL. Younger people less racist.
  • VoGhost None of the commenters who won't buy from China think twice about getting their oil from Saudi Arabia. They may even be filling up with Venezuelan or Russian petroleum, for all they know.
  • Johnny ringo In a word, no-the usual Chinese business model is to invite foreign companies into China as a joint venture, insist on a 49% share in the company-along with technology transfer and then push the foreign partner out and take control. And now with all the sabre rattling going on between the United States and China over Taiwan and the South China Sea and the possibility of a war, I'm not giving any of my money to the Chinese.