Tech Stuff

Intermittents -- Now you see them, and now you don't

A dangling/sloppy wire harness is a sign that someone has tampered with the harness (missing mounting tab or clamp, etc.). An unsecured harness can lead to heat damage, chafing or vibrational concerns at connections.
<p>A dangling/sloppy wire harness is a sign that someone has tampered with the harness (missing mounting tab or clamp, etc.). An unsecured harness can lead to heat damage, chafing or vibrational concerns at connections.</p>

Intermittent; it is a word every service writer hates to hear. How do you diagnose a problem when it isn’t happening? How do you tell the customer that there is no flat rate for this type of repair? What tools are available that can genuinely help solve this kind of problem? If finding and solving an intermittent problem can be time consuming and frustrating for you, don’t forget that it can also be expensive and frustrating for your customer. We all know that there just has to be a better way; the question is, what is it?

While there are no easy solutions, there are ways to address these kinds of problems. There are several important starting points. First of all, you must genuinely understand how the system is supposed to work. Your diagnosis will depend on understanding what the systems is supposed to do, what information is required for the ECM or BCM, and then what actions the system is supposed to take to accomplish the desired performance. The reality that this is a little different for every make, model and sub system is no help, but it is the truth.

Secondly, working with your service writer, you must gather the best information the customer can give you. In a normal repair, the solution is obvious or nearly so.

We all know that trouble codes don’t cover everything and can even lead you astray. Still, they do help a lot, and we’d all be stuck without them. When the problem is something that only happens part of the time, the circumstances of when and how it happens are critical. Some techs may find it useful to get the story straight from the vehicle’s owner (also known as the “horse’s mouth”).

A third part is your knowledge of what can cause intermittent symptoms. There are reasons behind these types of problems. You need to know what can cause an intermittent, what it looks like when you see it and what possible techniques can be used for reproducing it. You may find it very useful to use the Internet and automotive data banks such as iATN. Sometimes there really are vehicle make and model histories that can be useful in dealing with that “tough dog” problem in front of you.

There also are tools that can help. Some of these are already in your tool box, while others are the special tool box used by electronic technicians to service computers and industrial electronics.

There are also tools that might be helpful, but are so expensive and out of reach that they might as well not exist. In the end though, it will be your knowledge, your patience and your diagnostic skills that will solve the problem and send a happier customer down the road.

Types of intermittent problems

Intermittent issues can be divided by type and cause into multiple categories. There are two values in pointing this out to you. The first is that a logical, organized approach to trouble shooting is almost always the best policy. The second is to push the point that not all intermittents are electrical gremlins. An organized approach, that doesn’t ignore any possibility, is the best and even possibly the only way to get to a solution. Anything else is pretty much guesswork.

When you hear the term “intermittent” it would be easy to say, “Oh yeah, I know what that means.” The truth is that intermittent problems cover more ground than you think. It could be a battery that occasionally goes flat, but it could also be a lean surge.

To be an intermittent does not mean that the problem has to be electrical. An intermittent is anything that works part of the time but doesn’t work under one circumstance or another. One little nuance worth mentioning here is that you do have to know what normal performance is, in order to understand what represents “broken.”

One customer complained that every time he took off from the parking lot, the doors would all of a sudden “lock.” Another fellow complained that his brakes rattled and vibrated when coming to a stop in the wintertime. There are so many new features like Lane Departure Warnings (vibration in the steering wheel) that can seem like an intermittent defect simply because the driver isn’t expecting the vehicle to behave that way.

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