The Refrigerator Light - explaining intermittent diagnostics

Gonzo · July 4, 2015

The Refrigerator Light

Did ya ever find yourself at the service counter trying to explain to a customer how you diagnose an intermittent problem? I know I have. Intermittent problems can vary and the explanations of these problems are just as diverse as the problems. Typically, I’ll ask the standard questions: When does it seem to happen most often, how often does it occur, is it more likely in the morning or afternoon, and does it happen when the engine is cold or hot? Those type of questions. The usual answer in most cases is, “I don’t know”.

The big issue is that a lot of people don’t understand that even though they have seen a failure, and the fact that it doesn’t occur very often, doesn’t mean the mechanic is going to be able to find it without some background or investigative research. Take for instance this guy who came in and told me his car doesn’t start. I asked, “Where’s the car? I’ll have a tow truck pick it up?” His answer, “I don’t need one, I drove it here.” Then, of course, I’m back to the questions again, “So, when does it not start?” I’m confronted with the typical answer, “I don’t know”. The more I tried to dig into the history of this “no start” condition the more “I don’t know” seemed to come up. At best the only clear cut answer I got was that it did it once last summer. (This is no help at all nearly a year later.)

Apparently this guy (along with many others) was informed there is this magical diagnostic tool that can not only tell the date and time of a past failure, but can also predict the future demise of any component in the car. So, now my “intermittent” explanation is side tracked with explaining that there is no magical machine. Eventually, I went through the normal “intermittent” spiel, and how duplicating the failure was the most appropriate method beyond looking at the numbers and PID’s on the scanner. I could use a travel recorder that will record pertinent information and give it to the customer to drive around with it hooked up to the car for a bit, but since the last failure was the previous summer I don’t think leaving the recorder in his car would do any good. Since that’s not really an option, I did my best to explain how I diagnose intermittent problems with something that most people could relate to -the refrigerator light.

“Let’s say your refrigerator light is the intermittent problem. It’s working now, and should work every time you open the door, but at some point it’s not. The bulb could burn out, or it may get jarred loose and intermittently come on. But, the very next time you open the door the light may come back on, even though it didn’t come on the last time. So, if you stand in front of the refrigerator and can tell me when it’s going to fail, or know precisely when the next swing of the door in which the light isn’t going to work, then it’s no longer intermittent, but predictable,” I told him, “So, before you swing that door open for that midnight snack, ask yourself this, “Is the light going to be on, or is this the day it burns out?”

Keep in mind those light bulbs last a long time, and even if you are the type of person who calculates the exact hours of use that the bulb is predicted to last, I doubt you could ascertain the appropriate day and time it will actually occur. Without a pattern, or being able to duplicate the problem, a lot of intermittent problems are just plain impossible to solve. You need facts, figures, and a good diagnostic background to tackle them. And yes, with the right information they can be solved.

Everything has a fail point; everything has a lifespan. The problem is I can’t predict a failure any more than the man on the moon can. Oh sure, I can take a few “SWAG’s” at it, and I might even have some insight on which parts will fail more often than the next, but that doesn’t mean I can find the reason your car failed to start nearly a year ago.

This guy seemed to understand and was happy to keep track of his car under the conditions it failed to start. In the meantime, we did an overall checkup of his car just to be on the safe side. But, I did warn him even with the best checkup out there, it doesn’t mean you’re free from a failure. It could be something that was totally unexpected and wasn’t seen during the checkup, or it could be something that is internal in a computer that you can’t see at all.

A few days later he was back. He had this grin on his face a mile wide. There was something he was dying to tell me. “Did it finally not start for ya?” I asked. “Nope, car is fine,” he said.

“So what brings you here today?” I asked.

He jokingly told me, “My refrigerator light burnt out last night. I thought of you when it happened. I was standing in front of the refrigerator, and before I opened the door I would make a bet with myself whether or not the light was going to be on or off.”

Peculiar to say the least, someone actually drove across town to tell me about their refrigerator light, but now I was curious. I wanted to know the outcome. “So, did ya win your bet or not?”

“I lost,” he said, “but the car has been running fine since you did the check out. In fact, I’ve got the wife and kids playing the “Guess if the refrigerator light is going to be on game” too!”

Apparently, I’m a big hit around his house. Who would of thought explaining intermittent diagnostics would be fun for the whole family. This just proves that it really does take all kinds to make the world go around. I’m just glad I chose the refrigerator light as the example and not some other common household fixture or appliance.

Now, I’m wondering, has this ever happened before, and how often? Maybe it happens more in the morning or late in the afternoon? My best diagnostic answer, “I don’t know.”

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