Avoiding Common A/C Service Mistakes

Jan. 27, 2021

When it comes to customers and their vehicles, the few things that seem to matter most to them is that the entertainment system is working correctly and their HVAC system is doing its job. Customers rely on their creature comfort amenities to get them from one place to the other. It seems that most customers don’t mind spending the money on these items as they feel they are getting more for their money as opposed to say repairing that leaking water pump or an axle boot that has a split in it. If the radio or the air conditioning stops working for whatever reason they notice it immediately as they will feel “inconvenienced.”

When it comes to A/C service, we as technicians need to be aware of the potential service mistakes that can happen when servicing your customer’s air conditioning systems. Not paying attention to details will not only increase the cost of the A/C service but it will also raise the temperature of your customer’s expectations. 

In this article we are going to look at a few common mistakes that can happen when servicing an A/C system and procedures we can use to avoid those costly comebacks that every technician dreads.

Fig. 2: Mastercool electronic leak detector and sensor. (Courtesy of Southeast Mobile Tech)

First and foremost the tools and equipment that are used to service the modern HVAC system must be in proper working order. This can range from recovery and recharge machines, leak detection tools as well as manifold gauge accuracy and scales that are being used to measure the proper amount of refrigerant that goes into each vehicle. (Fig 1) (Fig 7) If any of these are found to be defective then the repair won’t be accurate which could impact a properly functioning system to not work to 100% capacity. Just having an inaccurate manifold gauge could skew your readings to an improper charge amount. Some of these systems are dialed down to a couple of ounces for an accurate charge of either under filling or over filling the system. 

Fig. 3: DPS electronic leak detector. (Courtesy Southeast Mobile Tech)

The same goes for that leak detection tool. Whether it’s an electronic tester with a sensor that has debris built up on its tip or the sensor that was damaged by some other source, finding leaks could provide a very difficult outcome, or worse it might miss a suspected leaking area all together. (Fig 2, Fig 3) Also the leak detection method of using infrared dyes as a source of finding a leak can fail at times. 

I know this is true as it has happened to me. As an example, I began to use my oil dye on a vehicle to locate a leak and the dye I had hadn’t been used in a very long time. I injected the dye and it actually didn’t show up as a dye at all. I knew the area of the leak but the dye somehow lost its ability to work properly. I purchased some new dye and the dye worked fine. I am guessing that the dye I used quite possibly had a shelf life and with it sitting around in different types of temperature conditions this might have neutralized the chemicals in the dye from working as they should have. 

That’s just one example. Paying attention to your equipment can go a long way to achieving a proper repair and avoiding some of the headaches along the way.

When servicing your customer’s vehicle, other than the proper tools needed to do the job, you need to have an accurate service information system with you and an idea of how the system is designed to work. 

Also it’s a good idea to ask the customer about prior repairs that have been done to the vehicle and if possible look at the previous service history on that vehicle. Gathering as much information as you can will not only help guide you in the direction you need to go but will also help save your customer some money as well. 

As some of you know, some do it yourselfers will try to fix their A/C systems themselves. Since there isn’t any special license to buy certain kinds of refrigerant, they can pick up what they need at any convenience store or big box store. Some of the refrigerant that is sold will include some leak detection sealer already in the refrigerant. 

This sealer is supposedly designed to stop leaks from the inside of the A/C system, presumably to avoid the costly repairs the service facility will charge. However, since the sealer is designed to stick on the internal components of the A/C system in the area of the leak itself, it can present a problem when you go to recover the vehicle’s refrigerant using your recovery machine. 

Where do you think that sealer will go next? It will go into your equipment and will stick to the valves and solenoids of your recovery machine and that will impede the operation and possibly damage your equipment. Having your machine repaired because of refrigerant sealer contamination can be very costly (not only the cost of the repairs but the cost of down time that keeps your machine from doing any other A/C servicing). 

Fig. 4: Nueatronic refrigerant sealer identifier tool. (Courtesy of Neutronic Automotive)

Fortunately, there are tools that can check the state of the refrigerant that is in your customer’s vehicle and alert you that the system could be contaminated before you hook up your equipment. An example is shown here. (Fig 4) It may cost a few dollars for the tool but it could save you hundreds of dollars in repair costs. It is critical to investigate what you are working on before exposing yourself to these situations. 

Another tool is a refrigerant identifier. These tools can check exactly what type of refrigerant is in the system you are servicing. Unfortunately there are some service facilities that are not using 100% refrigerant in the vehicles they are servicing and some can be harmful or even flammable, posing a risk to the service technician. It’s important to be cautious when starting your A/C service.

One of the biggest mistakes that I have seen while repairing an A/C system is the advent of an A/C compressor failure. The single biggest reason that an A/C compressor fails is a lack of oil in the system. 

Whenever you are servicing an air conditioning system and you are changing any component, you have to remember to make sure the system has the proper amount of oil required in the system and also the correct type of oil required for that particular system. 

Does this all sound familiar? It should, as we have to do the same for the engines that we service . Correct oil quantity and proper oil viscosity is just as important in an A/C system. Even though many replacement compressors state that oil is already added, it’s a good practice to check the oil level yourself before you install that compressor. 

I like to drain the oil that’s in the new compressor and measure the oil that came out. Is it the correct amount? Does it look like clean fresh oil? For peace of mind I like to fill the compressor up with the correct amount and correct oil on my own.

Another costly mistake is not knowing why the compressor failed. Did the internal bits of the compressor start to disintegrate and distribute pieces into the system? Don’t install that replacement compressor without knowing this first. If the compressor failed internally you now have a contaminated system that needs to be flushed out or even replaced. 

All those contaminants will block the areas that the refrigerant needs to go which will in turn decrease the performance of the new compressor and more than likely lead to a premature compressor and avoidable failure. Fig 6. The A/C systems on today’s modern vehicles have passages that are very small. The least bit of particles in the system will prevent the other components from doing their jobs as well. 

Other costly mistakes with regard to compressor failure would include the drive belt, which can impact the front compressor clutch bearing by over tightening the belt. A belt that is under tightened will allow the compressor to operate at a reduced speed and will affect how the refrigerant pressures will be on the system. A loose belt will wear out a lot quicker and more than likely create some unwanted noise under the hood. A compressor that is not mounted correctly will cause a vibration to the compressor and over a short period of time will damage the internal components of the compressor. 

A compressor that’s over tightened or not tightened evenly can stress the compressor housing and reduce its life. It might even create a belt alignment issue as well. Some mounting issues I have come across include the lack of the small round mounting retainers or alignment dowels that help keep the compressor mounted in place. 

Sometimes the replacement compressor does not include the mounting guides, requiring re-use of the original guides. Frequently this is overlooked. Always perform a good visual inspection of the mounting bosses once the old compressor is removed. Look for cracks in the mounting bracket, as well as taking a look at the mounting bolts themselves. When a compressor does fail it is extremely important to inspect the rest of the system. 

A failed compressor is the single most costly failure on an A/C system. It will take out anything in its path. The single most costly mistake that you can make is not conducting a complete analysis of the failure and to catch any potential issues after the fact. Remember when I said customers don’t mind spending money to keep themselves comfortable? This just might challenge that thought process.

Another costly mistake in diagnosing an A/C system is overlooking the basics. Remember, if the engine isn’t working the way it’s designed to then the A/C system will follow suit. An A/C system operates on the basis of temperatures and pressures. If for any reason the engine isn’t building up the correct temperature the A/C system won’t work efficiently. 

The engine’s cooling system has to work properly in order for the A/C system to do its job as well. An engine that is overheating and has a cooling fan that is malfunctioning, could be using that same cooling fan for the A/C condenser as well. Obviously, a cooling fan cools the radiator to allow the engine’s coolant to stay at the correct temperature. 

That same cooling fan is also needed to keep the refrigerant temperature low and thus reducing the excessively high pressure that can build in the condenser. Making sure that the base cooling system is working as designed will aid in your A/C system diagnosis. That is a crucial step that needs to be made in your diagnostic procedure before you continue with your next step. Another costly mistake while performing repairs on an A/C system would be adding the exact amount of refrigerant that is called for. 

If a system calls for say eighteen ounces, and you decide to recharge the A/C system using two of the one pounder cans (technically they are only twelve ounces each), then you would be overcharging the system by four ounces. That may not seem like a lot, but that can raise the pressure in the system to the point where the refrigerant will start to boil, placing undue strain on the compressor as well.

Fig 5: Image of a failed compressor on a Toyota Prius. (Courtesy of Prius Chat)

This type of scenario happens many times and especially with the do it yourselfers out there. In the case of A/C service, more is definitely not better. (Fig 5)

A/C system service is one of the best and most profitable services that a shop can provide. The customers expect to be comfortable and most are willing to bite the bullet when needed to stay that way, as they tend to place great importance on the comfort level. 

Making sure you follow the service procedures and specifications to the “T” will make A/C service proceed more smoothly, keeping both customers and technicians alike within their comfort zones.

 Fig. 6: A/C manifold tool. (Courtesy Southeast Mobile Tech)

About the Author

Edwin Hazzard

Edwin Hazzard owns South East Mobile Tech in Charleston, S.C., which is a mobile diagnostic and programming service providing technical service to many automotive and body repair shops. He has 38 years’ experience in the automotive industry. He currently is an automotive trainer, a board member of TST (Technician Service Training), a member of the MDG (Mobile Diagnostic Group), a member of the Professional Tool and Equipment advisory board for Pten magazine, a committee member of Nastaf, and is a beta tester for multiple tool makers.