Friday, 15 September, 2006
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.