This Equipment Focus article delves into HVAC (Heating, Ventilation, and Air Conditioning) diagnostics and servicing, emphasising the need for meticulous attention to detail. Explore strategies to enhance technician efficiency, while also avoiding costly comebacks. 

Exploring HVAC Evolution: From Creature Comforts to Cutting-Edge Servicing

In this month’s Equipment Focus, we dive into the world of HVAC diagnostics and servicing, where attention to detail is key.

Author: Keith Wray
Snap-on® Diagnostic Training Manager


Creature comforts definition: those small indulgences that contribute to bodily comfort and ease, encompass pleasures like a hearty meal, a warm home, an ice cold drink or a refreshing shower.

I am grateful to have two such comforts in both my personal vehicles and my home. Interestingly, the availability of features like air conditioning and factory heaters in vehicles hasn't always been the norm. In fact, it wasn't until the 1960s that air conditioning became common in homes in the US, and more recently in the UK.

Even more surprising is the fact that it wasn't until 1962 that hot water-based heaters became standard on General Motors vehicles. Prior to this, heaters were optional in the automotive industry until Motor Vehicle Safety Standards mandated windscreen defrosters in 1968, making heaters a standard accessory in all cars.

My first vehicle, a 1951 Chevrolet pickup, boasted air conditioning, albeit a primitive 250 model. It was a simple affair: open the two-wing windows and cruise at 50 MPH. Interestingly, wing windows, also known as wing vents, fell out of fashion by the 1980s as air-conditioning became more prevalent. However, my old truck lacked a heater, so I relied on an old quilt for warmth during longer trips (If I had a date in the winter, I would bring an extra quilt!). Our ancestors had their own creative solutions for warmth, including heating up bricks and placing them in the cab for a little extra comfort. Optional add-on heaters, such as coal stoves, petrol heaters, and exhaust heat exchangers, were also common in the past.

The introduction of air conditioning in vehicles dates back to 1939 when Packard introduced a primitive form of the technology. However, it wasn't particularly effective, with the evaporator and blower system taking up half the boot space. Additionally, the lack of an adjustable thermostat meant it operated at full blast or not at all, making it inefficient. Oh, and the cost of the system was £220, with the starting price for the car was £883. £220 in today’s money would be £4827

By the 1970s, air conditioning had become a standard feature in nearly all new cars, except for Datsun. Other imports would ship vehicles without air conditioning, with dealerships installing it as an optional extra after purchase. My early experiences with automotive work, including installing radios and air conditioning units, taught me valuable skills. Today, Heating Venting and Air Conditioning (HVAC) work can be highly profitable for garages and technicians. However, it's crucial to service these systems thoroughly to prevent costly comebacks, which can significantly impact profitability. In fact, comebacks are one of the biggest "profit killers" in the industry.

Case study: 2014 Chrysler 300

The customer states: "On hotter days the AC does not work as well as it used to when it was new!". 

The car has over 58,000 miles. Another big hint perhaps, The AC had been serviced at a discount repair centre. 

Diagnostic Strategy

  • Should we check pressures & vent temperatures 1st?
  • It’s 27ºC in the workshop
  • It’s 7ºC at the vent
  • Low pressure = 60 PSI
  • High pressure = 230 PSI

Both low and high pressures are high, aren’t they? So, what could cause that?

Consider refrigerant overcharge or air in the system as there was some cooling at the vent, right? Remember the customer said it wasn’t cooling as good as it used to, and had it serviced at “discount” centre? I have a feeling that it was overcharged and probably still has another problem.

Today’s vehicles call for much more accuracy when charging an A/C system. That is because they require way less refrigerant than ever before. Any system using less than 680 grams (24 oz.) is considered a critical charge system with an accuracy level of as much as +/- 15 grams (or +/- .5 oz) commonly considered tolerable.  Many manufacturers of AC equipment push the limit and use economy scales that would only have +/-15 grams accuracy. SUN® Air Conditioning Systems use scales with a +/- 10-gram accuracy to ensure critical charge vehicles do not get overcharged resulting in a comeback, or a no comeback like this case study.

Obviously, a complete recovery and recharge of the system is step number one.

Re-test results

  • Low pressure = 42 PSI
  • High pressure = 185 PSI

Both pressures are where they should be, only 3 degrees better

The temperature at the vent is only 3 degrees colder. It's not bad, but I bet on a hot day it would not be as cold as it “used to be when it was new.”  Could we have an air distribution problem?

Thermal Imager

Let’s look at a picture that will say a thousand words, using a Snap-on® Thermal Imager with the AC on max and the blend doors set on the dash vents, we grabbed this image showing the culprit.

Toward the bottom of the picture, we see two dash vents to the right of the steering wheel (see the green squares). Note the three defroster vents on top of the dash, (see the green circles.)  There should be zero cold air hitting that hot windscreen should there? The hot glass would warm that cold air up before it gets to the passengers. In fact, on hotter days this AC would not get as cold as it used to when it was new.

The blend door actuator is either bad or out of calibration which is pretty common on certain OEMs. Let’s get a scan tool and see what we can do.  

The screen captures from the Snap-on® ZEUS+ Diagnostic Tool show that there is a recalibration function that should solve the issue by making sure the blend door swings all the way closed. In the dash vent position. If the calibration fails it indicates a bad actuator or something obstructing the door.

To complete this job, as with any HVAC repair, I recommend replacing the cabin air filter, because restricted airflow is always a common culprit of an inefficient AC system.

Conclusion: In the world of HVAC servicing, meticulous diagnostic processes and precise servicing procedures are paramount. By prioritising accuracy and thoroughness, technicians not only enhance efficiency and workflow but also safeguard against costly comebacks. 

Ultimately, this dedication to excellence ensures enduring comfort and reliability for customers while driving profitability for your garage.

Here's some additional ways that SUN® AC Service Systems can enhance air conditioning servicing for your business:

Enhanced Efficiency: SUN® Air Conditioning Service Equipment streamlines the entire air conditioning servicing process, from refrigerant recovery to system recharging, reducing downtime and increasing the number of vehicles serviced per day. 

It's fully automatic operation allows technicians to multitask, from simply setting up the system and leaving it to run giving technicians the ability to attend to other tasks simultaneously, significantly boosting efficiency and overall productivity in the workshop.

Streamlined Service Process: With a SUN® Air Conditioning Service system, workshops can streamline their servicing process and improve overall efficiency. 

The automated operation of SUN machines simplifies tasks such as refrigerant recovery, leak detection, and system recharging, allowing technicians to complete jobs quickly and accurately. This increased efficiency enables garages to handle more customers and enhance their revenue potential.

Vacuum Procedures: Vacuuming is a critical step in air conditioning servicing, and these systems excel in this aspect. With a minimum vacuuming time of 20 minutes during recharging procedures and 40 minutes after component replacement, they eliminate moisture and air from the system thoroughly. 

This prevents corrosion and damage to integral components like the compressor, safeguarding against costly repairs or premature failure. Efficient refrigerant circulation is ensured, purging contaminants for improved system efficiency. 

Additionally, vacuuming aids in leak detection, allowing for early intervention to maintain system integrity and consistent cooling performance.

Precise Oil and UV Dye Management: These systems go beyond traditional methods by precisely administering the correct amount of oil and UV dye into the air conditioning system. Unlike predetermined volume additions, the automated process ensures that only the required dosage of oil and UV dye is present, tailored to the specific requirements of each vehicle. 

This meticulous control prevents over-pressurising the system over time, mitigating the risk of compressor failure. UV dye, when exposed to UV light, fluoresces, making leaks visible even in hard-to-reach areas. 

By avoiding costly compressor replacements, garages can enhance customer satisfaction and reduce expenditure for vehicle owners.

Preventative Maintenance: These systems integrate nitrogen pressure testing as part of routine AC servicing, enabling proactive leak detection and prevention. Combining nitrogen pressure testing with UV dye enhances precision in identifying leaks. The pressurised system facilitates the release of UV dye from any leaks, making them easily detectable under UV light. 

By identifying and repairing leaks before they escalate, technicians extend the lifespan of the AC system and prevent costly repairs and more importantly prevent comebacks. 

This proactive approach to maintenance ensures optimal AC performance and reliability, enhancing customer satisfaction and reducing long-term expenses.

Need to upgrade or add Air Conditioning Service Equipment to your garage?

Speak to your Local Snap-on® Franchisee or Technical Sales Representative for more information

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