Every repair order should include the four C’s. The four C’s of automotive repair are, complaint (or concern), cause, correction, confirm. As a technician, utilizing the four c system will ensure you repair a vehicle properly. Similarly, as a customer, looking to see that the four C’s are on your invoice will help ensure you are using a mechanic who knows the proper steps to repairing a vehicle.

We will use the example of a car overheating to demonstrate how to use the four c method. The repair order would say something in the realm of: “Customer states vehicle runs hot, please advise”. As a technician, your first step is to replicate the complaint. Whenever possible, quantify the complaint. Test drive the vehicle and watch the coolant temperature sensor. You can record the data, and add to the repair order, “Test drove vehicle, engine coolant temperature reaches 230 degrees Fahrenheit”.

Next you must determine the cause of the complaint. For this example, we will say the cooling fans are not coming on. The cause should be listed on the repair order, such as, “Checked vehicle to find, vehicle runs hot due to cooling fans not turning on. Checked fan motors to find them working. Checked power and ground to find power supply missing. Checked cooling fan relay to find relay inoperable”.

Next comes what was done to repair the vehicle. The correction should be clearly documented, “replaced cooling fan relay”.

Now is the most important step, confirm your repair has actually fixed the vehicle. Again, as a technician you want to quantify as much as you can. List any data found after the repair, in order to substantiate the fact that you have indeed fixed the car. “Test drove vehicle after repair to find engine coolant temperature now reaches a maximum of 205 degrees Fahrenheit”.

The repair order and invoice would then say, in total “Customer states vehicle runs hot, please advise. Test drove vehicle, engine coolant temperature reaches 230 degrees Fahrenheit. Checked vehicle to find, vehicle runs hot due to cooling fans not turning on. Checked fan motors to find them working. Checked power and ground to find power supply missing. Checked cooling fan relay to find relay inoperable. Replaced cooling fan relay. Test drove vehicle after repair to find engine coolant temperature now reaches a maximum of 205 degrees Fahrenheit”.

Now it is a fair amount of work to perform all these procedures, but following the four C’s will without exception ensure the vehicle is repaired correctly.

From a customers perspective, this very procedure is why mechanics charge for diagnostics. We are not only determining what is wrong with the vehicle, but we are also confirming the repair. Also, if you do not see the four C’s on your invoice, I recommend you start looking for a new mechanic. If you do spot the four C’s, you’ve probably found a mechanic worth holding onto.

From a technician’s perspective, this kind of documentation is the most valuable thing you can ever imagine when it comes to a dispute over whether or not your repair was valid. Furthermore, following the four C’s will almost without exception keep you from mis-diagnosing a car, or not fully repairing it, thus all but eliminating the dreaded comeback.