Refrigerant leak detection

Jan. 1, 2020
The average refrigerant charge in an older A/C system could be three pounds or more. Most passenger cars and light duty trucks today carry less than 20 ounces of refrigerant — barely more than one pound. So is efficient leak detection important

Efficient work in this area matters more as less refrigerant is used.

undercar a/c service mobile a/c service air conditioning refrigerant refrigerant leak detection repair shop training technician training A/C training automotive aftermarket The process of refrigerant leak detection took on great urgency with the adoption of the Environmental Protection Agency's (EPA) Clean Air Act in 1990. Section 609, the part of the act that applies most to the automotive community, requires service technicians to be certified in proper refrigerant recovery and recycling. The intent of the law is to lower emissions of gases harmful to the environment, in part, by requiring system leaks be found and fixed prior to recharging the system for normal use.

While volumes can be written on the environmental, social, political and financial ramifications of this law, in the end there is only one thing that really matters to us as shop owners and technicians — repairing our customers' vehicles correctly the first time.

Like other precious resources we value, the less there is of something, the more we want to prevent it from escaping. The same is true of automotive refrigerant.

The average refrigerant charge in an older A/C system could be three pounds or more. Today most passenger cars and light duty trucks carry less than 20 ounces of refrigerant —barely over 1 pound. One of the smallest capacity systems on the market today is the Toyota Yaris, which runs on approximately 11 ounces. A leak of just two ounces of refrigerant in this system will cause reduced performance, affect system lubrication and eventually lead to component failure.

So is efficient leak detection important to properly repairing your customers' A/C system? You bet! Just ask the next hot, sweaty and (dare I say) cranky customer that walks into your shop after their A/C system has stopped working and the outside temperature has skyrocketed.

Before we begin to talk about leak detection methods and techniques, it is important to look at the causes and types of leaks we will normally be diagnosing.

Causes of A/C Leaks

An informal survey of the top five refrigerant leak detection companies revealed their opinions on where system leaks occur most.
Top on their check list were holes in the rubber hoses, seals and gaskets of the system created by age, improper lubrication or wear. Heat and other adverse underhood conditions take their toll on rubber components causing premature aging, which leads to dried, cracked seals and hoses. Infrequent system usage and the lack of circulating refrigerant/oil that helps keep seals and O-rings pliable also is a concern. Compressor shaft seal wear, caused by lack of lubrication or externally by dirt also can cause leaks.

The next cause was just as obvious: physical damage, most notably stone or other debris damage to the condenser. From recent reports, this seems to be more of a problem with some vehicles, like late model Hondas, than others where the condenser is fairly well protected.

Next is normal wear and tear on the system. Depending on the climate in your area, your customers might run their air conditioning only a few weeks or months of the year or all the time. Road conditions, unperformed maintenance or just plain normal fatigue might cause broken or loose piping clips that allow pipes to flex at joints, hoses might chafe or abrade in engine compartment and fittings might loosen due to vibration or movement between system components when the vehicle is in motion. All of these have the potential to cause leaks.

The last common cause has to do with technician error: improper tightening/sealing of air condoning systems. While most technicians will do their best to not disturb refrigerant lines or components while working in the engine compartment, sometimes it is inevitable. When lines are disconnected, special attention needs to be paid during reassembly to prevent leaks. By not using new, properly lubricated O-rings and tightening fasteners using the proper tools, to the proper torque, leaks can and will occur.

Active Leaks vs. Passive Leaks

In the majority of situations leaks can be broken down into two types — active leaks and passive leaks.

An active leak occurs when the system is under pressure no matter if the system is running or turned off. Some difficult to detect active leaks occur only when the vehicle is in motion due to flexing of components as the vehicle drives down the road.

A passive leak normally occurs when the system temperature cools to ambient temperature after operation. Leaks occur as seals/packing, which might provide a proper seal between the components at full operating temperatures/pressures, lose their integrity and allow refrigerant leaks between two components as the components cool down.

Now that we know the types of leaks and the most likely spots to look, how do we find them?

The Latest SAE J2791 Electronic Detectors

There is no doubt that electronic detectors are handy for quick inspections and for locating hidden leaks that cannot be seen with UV light. Detectors produced prior to the adoption of SAE Standard J2791 in 2007 had the capability of detecting a joint leak of 14g/year at a probe distance 1/4 inch. False triggering, a big issue to technicians, was numerous with chemicals typically found underhood and there were a wide range of related issues including the speed at which the probe was moved across the target.

Bob Savasta of Spectronics/Tracer Products is a big proponent of the new detectors. "The J2791 electronic detectors offer increased sensitivity over their predecessors, while cutting down on the chances of false triggering," he says.

Since the adoption of the standard, electronic detectors are sensitive to leaks of just 4 g/yr at a probe distance of 3/8 inch. Probe speed has also been increased 50 percent from the recommended 1 to 2 inches per second. False triggering, a big issue with older detectors has been addressed. There are 15 chemicals on the SAE J2791 false trigger list. A J2791 detector will not false trigger on engine oil or transmission fluid. As for the other 13 chemicals, you'll have to read the owner's manual. Fluids like windshield wash, spot and stain remover, penetrant, trim adhesive, brake clean, silicone, hand cleaner and others might still cause false triggering.

"The latest generation of electronic detectors, can detect leaks so small that in some cases they may find A/C system leaks that are considered 'normal' from the factory," according to SPX/Robinair's Tim Wagaman. But, he admits, "Since using leak detectors that are compliant with SAE J2791 is not mandatory in automotive service, the new standard has had little impact. We still sell leak detectors that meet both the new SAE J2791 and previous SAE J1627 standards."

In order to clarify proper electronic leak detection procedures using the new detectors, the SAE Interior Climate Control Committee, chaired by Ward Atkinson, currently is reviewing SAE Standard J1628 — Technician Procedure for Using Electronic Refrigerant Leak Detectors for Service of Mobile Air-Conditioning Systems — and will be issuing new recommendations soon. This means that technicians will not only have the latest tools to find leaks but also the best methods as approved by SAE.

Are Electronic Detectors Enough?

So you just bought an SAE J2791 approved leak detector and your first A/C leak comes into the shop. Will your new equipment find the leak? Maybe not according to Barry Harris of Bright Solutions.

"Regardless of the cause of a leak, different leak detection equipment is suitable under different circumstances, even though the process of leak detection is the same," he says.

A strong case can be made for the other method of detection, UV dye, as some OE manufacturers choose to add dye to their new vehicle systems on the assembly line. Proponents point to the fact that dye provides positive proof of a leak and it's exact location. Harris contends, "Electronic detectors sense the presence of refrigerant."

If there is air movement or if there are multiple leaks, refrigerant can be circulated in the engine compartment leading to false triggers. "Electronic detectors can not be used when the vehicle is running for the same air flow reasons," agrees Chuck Abbott of U-View.

The best method ultimately depends on the type and size of the leak, and where the leak is located. A combined electronic detector/UV dye approach was recommended by most detection manufacturers and just might be the most efficient. If a few minutes spent sniffing around hoses, seals and components does not turn up the leak, then dye can be injected and the customer asked to leave their vehicle or return with it at a later time.

"Dyes and electronic detectors both have their advantages, but in the end the method that works best is the one with which the technician works most efficiently," Savasta concludes.

Remember, that hot, sweaty and potentially cranky customer is waiting.

Jim Marotta is a freelance writer with more than 17 years’ experience in the automotive industry. He currently works as a technical writer for

Sponsored Recommendations

Best Body Shop and the 360-Degree-Concept

Spanesi ‘360-Degree-Concept’ Enables Kansas Body Shop to Complete High-Quality Repairs

Maximizing Throughput & Profit in Your Body Shop with a Side-Load System

Years of technological advancements and the development of efficiency boosting equipment have drastically changed the way body shops operate. In this free guide from GFS, learn...

ADAS Applications: What They Are & What They Do

Learn how ADAS utilizes sensors such as radar, sonar, lidar and cameras to perceive the world around the vehicle, and either provide critical information to the driver or take...

Banking on Bigger Profits with a Heavy-Duty Truck Paint Booth

The addition of a heavy-duty paint booth for oversized trucks & vehicles can open the door to new or expanded service opportunities.