Climate Control Diagnostic Process

By Bob Pattengale

Every Technician needs to have a diagnostic plan. The primary goal of the diagnostic plan is to prepare the Technician to solve the problem at hand. The plan may not work on the first try, but it will create very useful road map. To start, review the customer issue(s) and make sure to have the ticket from the service advisor. Most of the time, the response will be pretty vague like the A/C is not blowing cold air or the A/C makes a loud noise. Whatever the case may be, the Technician needs to duplicate the issue.

What if I can’t duplicate the issue?

If you cannot duplicate the problem at hand? In that scenario, this is where the process immediately stops. The issue needs to be replicated with 100% certainty. If you can’t duplicate said issue then it’s time to gather more information from the customer. Ask them how long has this been a problem, can they explain the issue in more details, and has this happened before? Often, these elusive phantoms are something that the consumer doesn’t understand. The system and the customer have different expectations. There’s nothing wrong with the system it’s how they’re using it. After talking to the customer, if the issue cannot be recreated then it’s time to talk to the service advisor.

The service advisor acts as a liaison between the mechanic and customer. The service advisors’ job at this point is to try to work out the problem step by step with the customer. If that fails, then it’s time to have the customer recreate the scenario in your shop. Take the vehicle for a test drive, have the customer show you or your service advisor what happens step by step. Accuracy is crucial at this step so take your time.

What part of the system is affected?

In the case of Climate Control, we have several different sections. We have the AC system, air flow volume, and air flow delivery. Then there are the mode doors which takes care of the directional side. There are more sections to a vehicle but as a mechanic you need to break it down into sections. These sections will create a direction to go in. Next, its time do the research. Make sure there is a solid understanding of that system with 100% certainty. Check the Technical Service Bulletins, look for any reprogramming or reflashes. Remember to not confuse TSBs with recalls. TSBs are issued from the vehicle manufacturer when there are several unprecedented issues. Do not guess your way around the vehicle either. There is no shame in researching the system to better help a customer. Customers are not there to idly chat, they want their car fixed the right way on the first visit.

Diagnostic Planning!

Now that you’ve mapped out and researched the problem it’s time to duplicate the issue at hand. Carefully retrace the customer’s steps with your equipment and scan tools in tow. Upon duplication, the section creating the issue will present itself. Knowing where the testing positions are to use the scan tool and attack the issue head on. Let’s assume that during the research phase it’s determined need to recalibrate the mode doors. Use your scan tool to perform a recalibration or can you turn the compressor clutch on and off.

The Diagnostic Plan Failed?

Playing devil’s advocate, what do you do if the diagnostic plan goes awry? What if there are no proper tools to get around that particular problem? What if there is a certain point this compressor clutch will not turn on or off? Going through the entire test and double checking the work.

Thankfully, that is where the diagnostic plan comes ahead. Bring in some extra eyes and show them what you did. Your diagnostic strategy is valuable. It will allow others to retrace your steps to see where they went wrong and fix it from there. Others can retrace it and fix the issue. Inthe end, if you go hacking away at the problem that you don’t have a plan for your just going to get stuck or worse.

Related Course

Bosch Advanced Climate Control Systems

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The days of simple air conditioning and heating repairs are long gone, which means the strategy for diagnosing these systems need to change. Today’s climate control systems are fully integrated, using a complex vehicle network, with shared modules, sensors and actuators. The answer for the customers concern could be a simple sensor failure or a stuck actuator blend door. This session sponsored by Bosch will help you develop a solid strategy for diagnosing the complete system, which will ensure the issue is diagnosed accurately and efficiently the first time.

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