You are already aware a good technician uses all his senses: he touches everything, looks everywhere and asks many, many questions. But first and foremost, the number one sense a good technician has is good common sense. With today’s...
You are already aware a good technician uses all his senses: he touches everything, looks everywhere and asks many, many questions. But first and foremost, the number one sense a good technician has is good common sense. With today’s complex vehicles, you first start by inspecting all components, wiring and connectors. On many occasions, customers will drive into your shop with an intermittent problem.
You’ve seen such problems before and you know that because they are intermittent, that can be difficult to solve. Your customer, however, expects that you can solve the problem in a timely manner. Now the question becomes, what do you do next?
Let’s look at some possible solutions, only one of which is the correct one:
– Spend 20 minutes on a quick diagnosis. Since the vehicle will probably not show any problem, you hand the car back to the customer, with the same latent problem. You hold onto the hope that you will be on holidays when the customer shows up again.
– Order a new ECU (no matter which one) and tell your customer there is a fair chance that the problem was cause by this defective part.
– Ask your customer questions, dozens of questions, in order to understand what is going on when the trouble happens. From the answers you get — and the answers will differ with each customer — you will soon begin to focus your investigation to certain areas. And if nothing happens, you are left with a complete visual inspection.
The third option is the right solution. If
you picked one of the first two, please don’t
Take time to look carefully
Now, what must you look for? Connectors, wires, terminals and grounds. Did you know that micro rust can affect a male or female terminal? In fact, road or engine vibrations can cause slight friction between the connectors. With time, a miniature separation only visible with a microscope can cause a resistance in the circuit. That simple resistance can trigger a system malfunction.
By the same token, unplugging and plugging again all the connectors can give a new life to the system for a few months. So, when you unplug a connector (Figure 1), make sure you measure the tension between male and female with the proper adaptor (Figure 2). If the tension is normal, apply a small coat of dielectric grease. Some manufacturers recommend using a terminal rejuvenator because this type of acid makes a perfect contact.
Close to the ground
Another issue with ground terminals comes from the fact they are linked to the body after they roll out of the paint shop, like this car seen in Figure 3. Turning the ignition sparked the engine. After questioning my customer (when, where and how), I had the feeling the problem was indeed a faulty ground. Now, how did that feeling originate? First the customer told me the problem was the starter. In fact, this information from the customer set me on the wrong track. A few questions later, I found out the whole vehicle blacked-out instead of just the starter. So, to recreate the situation, I turned on all the accessories. No start this time. I lost everything: starter, dash lights, HVAC, you name it. I put a booster cable between the battery negative and a good ground: Eureka! Sandpaper and grease did the job to repair the ground and leave another part in the box (picture 3).
I had this other case of a faulty ground between the vehicle body and the battery, but the symptoms were different than mentioned above. When the customer steered his truck, the lights in the dashboard would blink. For other vehicles, it could light the ABS warning indicator or simply cut off all lights. Needless to say, for one problem, a technician can find more than one symptom, and always intermittent.
My last starter problem was one that finally led to changing the starter. Again, when inspecting and checking for the problem, the vehicle was starting just fine. A thorough visual inspection of all components showed some rust on the starter’s main wire leading to the starting system, which was causing a power intermittence problem.
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