Friday, 15 September, 2006

Idiot Lights

Posted in Automotive at 1:13 pm by glpease

The dash of my GTi is not unlike the dash of most of today’s cars. It is populated by a limited number of actual instruments, speedometer and tach, and a byzantine array of iconic indicator lights, most of which, you’d rather not see illuminated once under way. One of them looks like a little battery, complete with a + and – terminal. It is there, supposedly, to tell you when there’s something wrong with the electricity. I’ll get back to that one in a bit.

Years ago, cars had gauges to tell the driver things about the condition of the stuff under the bonnet. An oil pressure gauge reassured that lubricant was flowing where it should, and hadn’t dripped all out along the motorway. A water temperature needle swung to a specific point that you quickly memorized, and if it went beyond that point, or never got there, it was time to do some checking up. Sometimes, a voltage meter was fitted to show, in a real sense, the condition of the generator, voltage regulator and battery – the stuff that, coupled with starters, distributors and ignition coils, compels the motor’s heart to start, and continue beating.

Somewhere along the way, most of these instruments took a trip to Atlantis, and were replaced by the now ubiquitous indicator lamps, not so affectionately called “Idiot Lights.” No longer can we tell that something is going to go wrong. A glowing lamp simply informs us that something already is wrong, sometimes after we already know this, and that we’d probably better do something about it.

The little engine icon, with the cautionary word “CHECK” underneath, is the most uninformative of the lights. It tells you something’s wrong, but give no indication of what. It can be illuminated for something as trivial as leaving the cap sitting atop the pump at the last visit to the filling station, or it can indicate something amiss in the maze of sensors, hoses, and valves that form the emissions control system. The real information is stored as a code in the car’s central computer, and can only be read using a special scanner. There’s no code, as far as I can tell, for the engine having fallen out of the car, but even the most mechanically unaware amongst drivers would probably sus that one out rather quickly. How does one get to the code?

The enthusiast can purchase a hand-held scanner that reads the OBDII (On Board Diagnostics) code, and reports on various conditions that are recorded in the memory of the engine management computer, along with the fault code. These little scanners range from very simple devices that cost under $50, to elaborate multi-hundred dollar instruments that interface with a laptop computer, and can be used to monitor driving conditions, reset parameters in the ECU, and even reprogram alarm and window functions. Armed with one of these machines, a car owner can determine what went wrong, causing the light to come on. Once the repair is accomplished, the same device can be used to reset the code, extinguishing the light. If you don’t have one, it can be a trip to the shop, with a $100 bill in hand, just to get the information. Then, there’s the cost of the repair, if necessary. This can result in a pretty spendy gas cap.

Overall, these OBD codes can actually be quite useful, often providing some real information after the fact when an intermittent failure occurs, or when one piece in the complex puzzle that is the engine management system is slightly out of kilter. The lights, too, can give some clue as to what’s wrong, but usually only after it’s already wrong, not when it’s going to go wrong. (Remember the gauges?) This is all well and good, when the lights do their jobs.

Back to that little battery icon I mentioned. A couple weeks ago, my car was cranking a little sluggishly in the mornings. The day it almost refused to turn at all was the day I figured it was time to replace its 6 year old original battery. I ran up to the local parts store, and $84 later, returned home with a shiny new battery.

When things decay slowly, we don’t always notice, and that was certainly the case with the old battery. I didn’t realize its cranking power had decreased so dramatically, and had no useful instrument on the dash to inform me that things were going awry. Had that morning’s hard starting not clued me in, the battery would have just continued to decline until the car wouldn’t start at all. So much for the usefulness of the little battery icon; it never illuminated.

That’s only part of the story, though. Monday, I drove to the market. I’d just made it into the parking lot when my dash transformed into something akin to a discotheque light show, minus the mirrored ball. I was concurrently serenaded by a raucous cacophony of beeps and buzzes, and the engine un-cooperatively and unceremoniously ceased to run. Turning the key yielded nothing more than a click from the starter solenoid, and its rhythmic sputtering for a couple seconds, and then, nothing. Dead.

Okay, I’m a geek. I carry a voltmeter in the little tool kit that’s always in the back of the car. The battery read 9.2 volts, about a volt below what is necessary to keep the car’s electronics functioning at all. I watched as it started to climb, settling down at 10.4 volts. I got back into the car, turned the key on to what used to be called the “IGN” position, and looked at all the wondrous red and amber lights on the dash. The only one that was not shining like a beacon in the night was the battery icon. I guess since I already knew there to be something wrong with the charging system, I should have been happy not to be confused with redundant bits of information. But, a confirmation of my suspicions might have been nice.

Forty dollars later, the tow truck dropped the car in front of my garage. I connected my battery charger to the shiny new battery, and went in to cook dinner for company. The next morning, I could start the car. Measuring the voltage again, I found it hovering around 11.8 volts, rather than the 14+ volts that should be present with the engine running. Clearly, the generator was not doing its generating. Still, the battery icon was as dark as midnight. Strange.

Examining the schematics (I really am a geek), I note that the battery light in series with the electronic voltage regulator and the field coil of the generator. Brilliant. If the charging system fails, the thing that’s supposed to tell you it failed may not work – in fact, probably won’t work. If the voltage regulator is broken, or the brushes on the rotor are not making contact with their contacts, the light (really an LED) has no path to ground. Worse, if the light’s circuit itself is open, the regulator can not supply current to the field coil of the alternator, so the thing can not generate charging voltage.

I decided to test the light, just to be sure it really worked, so I wired the sense lead through a 470 ohm resistor to ground, and watched with some minor feelings of triumph and elation as the little battery icon lit up, a beacon in the afternoon. (There’s that geek thing again.) At this point, I could be fairly confident that it was, in fact, the alternator, unfortunately, a damn expensive part. I ordered one, picked it up, and a couple hours later, was back on the road.

I once thought that these indicators were called “Idiot Lights” because they were made for idiots. I now theorize that, at least in some cases, they are so-named for what they are, not what we may be. A simple voltmeter on the dash would have let me know in advance that something wasn’t right, and I would likely have saved myself the cost of a tow.

Maybe it’s not so idiotic, after all. Shops rely on people not being able to do simple things themselves anymore. Most modern cars are amazingly reliable, albeit difficult to work on, and it’s the maintenance routines and the small repairs, like alternators and batteries, that keep them in business. If I didn’t have that voltmeter in my tool kit, and a geek’s understanding of what to do with it, some shop would have been able to excise a fat wad of green from my wallet. Sorry guys. Maybe next time. In the meanwhile, I’m going to install a voltmeter on the dash, and while I’m at it, a real oil pressure gauge. I’d hate to see that little oil-can light up just after the motor had seized up and fallen out of the car.



  1. Richard H. Davis said,

    Gregory, in all seriousness, have you thought of writing for Road and Track? Your style is similar to the styles the mag likes. RD

  2. Allen H. said,

    Excellent post, Greg! I completely and whole-heartedly agree with you on this! I think that we have gone to extremes with cars these days. Often no effort is made for the ease of the consumer. Oil-filters on the inside back of the engine-block/ sparkplugs on engines that require tilting the engine forward to replace… the list goes on and on. Not to mention the overly complex Lan in numerous cars that are currently made. My little Dodge Neon may be one of the last cars without an on-board communications network which requires a serious computer to work with. I’m also pissed about the lack of guages these days. One of the silliest things I’ve seen is a “sports-car” with an automatic transmission and tachymeter. I can undersatnd a tachymeter in a standard (which I strongly prefer), but in an automatic? I guess I should give them props for putting in a guage at all, eh?

    The result of all this nonsense, is the loss of simple common-sense and ability when it comes to caring for an automobile. No wonder girls look at us funny when we talk about dip-sticks and tire-pressure. Their answer is often to take it to the dealer. [Just got a repair done for $40 on my GF’s muffler which would have cost over $150 at the dealer easy- a good machinist and welder is all you really need…]

    Motorcycles are getting much more complex these days as well. Luckily I have some that aren’t that complex… speaking of which, anyone want to help me pull an engine and work on a gear-box? 😉 [I’m a bit afraid of that one myself… guess I should just try it…]

    Excellent post, Greg- and a bit “damn straight”

  3. glpease said,

    Thank you, RD, for the kind words. I’ll give them a call, and see if they’re interested. 😉

    AH, the tach is in the car with an automatic for vanity purposes. See, you don’t want to red-line in top gear, blowing that little sewing machine motor apart at 160MPH. (I also find it amusing that so many speedometers range well beyond the top speed of the cars in which they are fitted. Granted, my little GTi is somewhat spirited, but the only chance it has of ever seeing 160MPH is in the belly of a cargo plane.)

  4. Trilithon said,

    Great point. Today is alot different than back when Cord was manufacturing fine automobiles. They even had a gauge to show the differential temperature! (for those of you to young to remember rear-wheel drive, it is also referred to as the ‘pumpkin’).

    As a pilot, I have a fascination for instrumentation and guages. I was on a training flight with an instructor once, and noticed a drop in battery voltage. I told my instructor, and turned back for home. Though this was not a life-threatening situation, it was a dangerous one, since the failure occurred in the air, about an hour and a half from home base. Since magnetos, which require no battery to generate power, keep the the engine running, it was not a big deal. Until it come to getting into an airport without a radio. I anticipated this, and shut down the airplanes power to conserve what little there was in the batteries.

    But the point is, I guess, is that if it hadn’t been for that guage, I would not have had battery power to turn back on when we got back home to communicate the problem, and to communicate with other aircraft that we had a problem. I wouldn’t have caught it soon enough with an idiot light.

    This does translate into a safety problem in a car, too. I have travelled the west, and there are some desolate areas out there. In some cases, nothing for alot of miles. If I inadvertently forgot to check my oil, for instance, and only had an idiot light, I could possible wander of into a dessert being dangerously low on the fluid. Personnally, I always carry extra fluids and a tire pump in my vehicles.

    I think the only ‘idiot’ in ‘idiot light’ are the vehicle manufacturers themselves. I am willing to pay a little extra for a car that is well instrumented. Perhaps the should emulate the old Cords a little, but within reason. Thanks for the post Greg.


  5. a11en said,

    Matt- totally agree with you! I’d much rather pay for more guages than a burberry interior. 😉 ha ha. [ok, a bit offbeat on that one!]… I think they have a new view of the car-owner as being total dolts. Unfortunately, if they keep removing us from the equation, it’ll be a self-fulfilling prophecy. Thank goodness you caught your problem in the air when you did!! Yikes!

    Greg- when I was a kid in HS and just learning to drive, kids would banter back and forth about top-speeds… you’d hear things like: “Well, my Mom’s Taurus can go 120!” 🙂 yeah right. 🙂 Totally agree with vanity purposes for the Tach as well. Maybe I’ll have to add a few guages to my little neon… it’s about to fall apart, but at least the gauges would tell me which part is about to come off. 😉

    Cheers everyone!!

    [thinking about sneaking in a pipe before I head in to bed- hmm.. odyssey may be calling…]

  6. George Dibos said,

    Anyone who TRULY yearns for guages has only to jump in a class 8 truck. When the full set is ordered, you’re encroaching on 747 territory: Turbo boost pressure, differential temps, engine water temp, engine oil temp, air suspension load pressure, brake system pressure, brake application pressure, RESERVE brake system pressure, tranny temp, e-system voltage, e-system charge rate, and on, and on. Row upon row.

    Let’s see, to keep this on topic, let’s ask why big trucks are so equipped, and cars are not? Could it be… that truck owners and operators actually think such information is useful? That maybe it SAVES big bucks, instead of costing SMALL bucks up front, to know the status of these components? And let’s not forget safety. Also a Very Big Consideration. So much that the drivers can be fined and/or (ultimately) end up in jail for not keeping track of the guages.

    It seems they’re so important that the federal government got involved, in other words.

    But cars only get the the blinkin’ lights, often wired in such a way they’re useless, and nobody cares.

    One of those things that makes you go, “Huh???”

  7. My only challenge is getting my wife to tell me that a light has even come on. Really, it’s not a joke. I’ve been burned twice. The first time was for oil, the second for brakes. I’ve given up trying to convince her that it’s really important to tell me about these things (read: it’s money that could have been spent elsewhere). I now drive her vehicle at least once per week. I also have it thoroughly cleaned each time I do this.

  8. iansforest said,

    Back in 1995 I was living in Fallbrook California with my ex-wife in a 2 br apartment just off of Ammunition Blvd. Our vehicle at the time was a beautiful Red 1987 Volkswagen Rabbit Convertible that I had purchased with a portion of the cash that she and I had received from our wedding war chest.

    One fateful Friday morning before I left for work (via carpool) I left money on the counter and instructions for my xwife to get the oil changed, which was advice given from a friend who had a mechanical mind with cars- as I do not.

    Well the little lady instead of taking the car in to get the oil changed decided to go to the grocery store and stock up on all of the necessaries that we would need for our weekend road trip down into Baja California/ Mexico and what happened? The motor seized up on the highway and it was far into the evening when I was finally able to get out to her on the highway where the car had been done in. It was a sad end for such a lovely little rag top convertible, even sadder was that it would cost more than the car was worth to fix it and we ended up selling her to a junk yard- the car I mean. The ex-wife was junked a year later;)

  9. As the owner of two Passats and the former owner of Jetta’s and Rabbit’s I can safely say that the current selection and function of the idiot lights that dot my dash are completely worthless and exist only to garner a $100 up front by the VW dealership. To add insult to injury they actually require that you fork over the diagnostics fee up front each and every time, there is no time limitation to this either. If after getting a VW diagnosis and having them do a repair if the light goes on a week later again they want another $100. Ridiculous. I’m glad I use an outside mechanic who, for one thing never charges for a diagnostic.

    All that said, I love my Passat Wagon, great car.

  10. Trilithon said,

    I will make one more comment on this subject. I am not opposed to idiot lights. But ONLY when then back up a gauge. The light should come on to say something like, ” Hey you idiot, look at your gauge!!!!!”

    This is a good use for them. A back-up system which alerts you that you weren’t paying attention.


    P.S. Please yell if you are paying attention.

  11. BTW, Most auto parts stores (AutoZone, O’Reilley, Advance, etc.) will read your diagnostic code for free. Really. Just pull inot the lot, walk into the store, tell them that you need the diagnostic code pulled and translated… Somebody comes out with a little portable reader, plugs into the port, reads the code, and tells you what it means. Of course, we all know that 90% of the time it’s the gas cap not being secured tightly…

  12. Ziggurat Vertigo said,

    I think that many cars have speedometers that exceed what the car can do so that there are fewer different kinds of speedometers for the manufacturer to stock (this helps make automobiles cheaper). I think the same is true of instrument clusters in automatics that have the tachometer. In the one-size-fits-as-many-as-possible scenario, it is cheaper to have one instrument cluster for the whole line even if some or many of the cars won’t need certain parts of it. My car has idiot lights for systems that it doesn’t have (they were options the original owner opted out of). I only know what they say because when the sunlight hits them just right you can read them without the benefit of their being lit up.

    I wish I had ABS brakes, but alas… Maybe it’s also the manufacturer’s way of teasing you about all the lovely extras you could have had if you weren’t so cheap.

  13. Steve Nordquist said,

    Good thing we’re in for Car Operational Computing as a Service (COCS), eh? Your sedan will call your cellphone (only while it is in the car!) and chew into an hourlong conversation at the end of which it will release a few gems about what’s operating well and what is not.

    If you don’t know how the whole Java for Mid-Engine cars thing works, you will of course necessarily buy a toolchain of things, for example Clipper Renewables>>iPhone>>Diagnostic and Log Application Subscription>>Service Appointment || Instrument Connectivity for Diagnostic Log Subscription (to your own car)>>Jackknife>>8kg mallet>>cheerleading>>Sony eBook>>Schematics>>Employee Agreement

  14. Steve Nordquist said,

    Of course these things will be called Customer Service Document 20-2398r
    For Acurugoiat Owners

  15. Loukianos said,


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