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Refrigerant check

By autotech-nic on May 4, 2018

Everyone knows the importance of using the right refrigerant, either R134a or R1234yf on newer vehicles, although a few high-end German cars have CO2 systems. But how do you know which one is inside, if it is a mixture or contains contaminants? Primalec says this is important for three reasons:

  1. The price of refrigerants is rising fast, R1234yf has always been expensive, and it is not unknown for R1234 systems to have been topped up illegally, unwittingly or deliberately, with R134a.
  2. The wrong refrigerant can lead to diminished cooling performance and in extreme cases, compressor damage.
  3. There can be legal consequences of using R134a in systems Type-Approved with HFO-R1234yf.

The only reliable way to check is by using a refrigerant identifier. Primalec has introduced two models. The Ultima ID analyser measures both R134a and R1234yf to an accuracy better than 1%. Its display gives a read out of the percentages of R1234yf, R134a, Hydrocarbons and air, and prints the result for your records. The Mini ID is also available for a quick check, giving a Pass/Fail result based on a minimum purity of 95%. The aircon specialist says these devices are not cheap, but they will save the potentially expensive consequences of getting it wrong.

R1234yf is designed to break down quickly in the atmosphere but it can also break down inside the A/C if it is contaminated, or if the wrong lubricants are used. Traditional PAG lubricants are not compatible with HFO-1234yf, special oils are needed. Primalec introduced its Snow Leopard branded HFO-PAG lubricants for R1234yf. These are ‘double end-capped’ HFO-PAGs, specifically engineered for R1234yf compatibility, correct anti-wear and extreme pressure performance. They also boast excellent performance in older R134a systems.

Leak detection

Detecting, locating and repairing refrigerant leaks is critical, because leakage is the most common cause of poor performance or of a non-functioning A/C. The leading leak detection methods are:

  1. Vacuum testing
  2. Glo-Leak UV fluorescent leak testing
  3. Ultrasonic testing under vacuum or pressure
  4. Pressure testing with nitrogen or with Nitro-Trace
  5. Electronic sensors
  6. Spray test leak locators

Your A/C service machine will have a vacuum cycle, during which a vacuum leak test is performed. On some machines this is automatic and if a loss of vacuum is sensed by the machine it will not proceed until action is taken. You must then find the leak, because you cannot legally charge refrigerant into an A/C which is leaking.

Glo-Leak UV is the most widely used because it gives you a visual indication of the leak source in the form of a bright fluorescent glow. It mixes with the refrigerant and the oil, and some will escape with the refrigerant leaving a trace at the leak source. Even in a discharged system, if the A/C already had the Glo-Leak UV inside before the refrigerant was recovered, the leak source should still glow brightly. If not you should use another method, but after repair add the fluorescent agent while re-charging. Many A/C service machines will do this automatically, and Glo-Leak UV gives you a quality control of the repair.

While under vacuum, an ultrasonic tester can be used to locate the leak by picking up the inaudible sound made at the leak source and translating it into an audible sound. This equipment can also detect leaks in a pressurised system and has the advantage that it can be used for a wealth of other vehicle diagnostics, including rainwater ingress leaks, worn bearings, electrical faults and more.

Pressure testing with nitrogen, or better with a detectable Nitro-Trace gas (95% OFN, 5% hydrogen), is now a recommended method  in most countries. It is often the only legal way to test a leaking system that has already been de-gassed. Leakage can be identified and located by:

  1. A pressure drop on the gauges indicates the presence of a leak.
  2. A hydrogen sensitive electronic leak detector can be used to locate the leak source
  3. An ultrasonic tester can be used to locate the leak audibly
  4. A spray on leak detector can assist in both the visual and the ultrasonic methods

Electronic sniffer instruments are designed to detect refrigerant gases. They are usually fitted with a probe to access tight spots. Some, such as Leaktronic-2, have a combination of audible and visual warnings plus a numeric indicator of the size of the leak.

Finally, an old fashioned bubble spray can help to confirm your diagnosis.

Primalec have been providing solutions for air conditioning since the late 1980s. For more information, please contact them by email at or by telephone on 01622 816955.



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Autotechnician is a magazine published nine times a year, delivering essential information to independent garage owners and technicians in the UK. Delivered both digitally and in print, autotechnician provides readers with technical, training, business advice, product and news, allowing our readers to keep up to date with information they need to run and work within a modern workshop.
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