In the last column we began to explore accurate electrical diagnosis with a Six Step Diagnostic Approach. To see the discussion on Step One: Verify the Complaint, and see all six steps in order, click here.
Now that you’ve successfully Verified the Complaint, here’s what you’ll want do next:
Step Two: Determine Related Symptoms
I consider this step to be the most critical step in the troubleshooting process. It serves to help you isolate which circuit, and which part of the circuit, has the problem that needs to be repaired. This step requires no tools, no tear down, and can be done without under-dash contortions!
The big benefit to this step is that it saves you crucial diagnostic time. If you’re interested in increasing diagnostic time, pay special attention to this step! Being focused and diligent during this step in the process makes your diagnostics fast, easy, and accurate.
By identifying related symptoms you can often eliminate unnecessary diagnostic procedures. In geographical areas like New England where we spread salt on the roads during the winter, and may live, or operate vehicles near saltwater, this step can uncover potential problem spots using a minimum of time. Corrosion often affects more than one system, sometimes without the vehicle operator knowing it.
What is meant by ‘related symptoms’? You will want to identify any other systems, functions, or circuits, which appear related to the problem you are trying to diagnose. Using a wiring diagram, (www.chiltondiy.com is one source for wiring diagrams), look to see what other circuits, or functions, are connected in any way to the circuit you are trying to troubleshoot. This will help you to determine points that the circuits have in common, and eventually isolate the problem to a particular section of the circuit.
Often you can use this step to determine if you have a power source, or ground circuit problem. For instance: when diagnosing a radio “doesn’t turn on” problem, identify what the power source (fuse) for the radio is. What other components share that source? Do all of these components work, or do just some of them work?
If you discover that all the other components connected to a particular power source work, what does it say about the power source? It’s working, right?! Now you don’t have to bother checking it. You just saved yourself a ton of diagnostic time…and you haven’t taken a tool out of your toolbox!
You will want to do the same thing with the ground points. What circuits share a ground point in common with your problem circuit? Do they work?
By pushing buttons, flipping switches, and turning knobs, you can quickly determine whether or not the power and grounds associated with your problem circuit are good. You may also discover other circuits that share connection points, splice points, or wiring with the problem you are diagnosing. Recognizing that there are other systems, or circuits, that are also not working, you are able to narrow your diagnostics to certain sections of circuits. Knowing an approximate area in a circuit where the problem is gives your diagnostics a definite direction.
In the next article we’ll discuss Step Three: Analyze Your Observations.