Refrigerant leaks are very common and create a lot of work for HVAC technicians. Lets look at the leak checking procedure step by step.
1. You will first want to verify if a leak is present, some leg work will be needed to prove this. Attach gauges to the system, if your gauges register zero pressure, it’s quite obvious a leak is in attendance. If the system is still holding a charge, some troubleshooting will be required to ensure that the system actually has a leak and there is not another issue present, such as a restriction, which can, on the surface look as the system is low on charge. Superheat and subcooling readings will be your friend in verifying a leaky system.
2. Once you have verified that a leak is present, give the entire system a visual inspection, the appearance of oil is a true indicator of a possible leak location.
3. If the system is completely empty, I would recommend adding nitrogen to the system and use a quality leak soap such as Viper Big Blu and look for bubbles, start with threaded fittings, Schrader cores, valves stems, and flares, they tend to be more prone to leaks than brazed joints.
4. If the system still has refrigerant, I recommend using a quality electronic leak detector such as the Testo 316-3 to track down the leak and then use soap afterwards to validate the leak location with soap bubbles.
5. Once you have tracked down and verified the leak location, you will have to communicate with the customer and put together a plan of action for repair.
Things to keep in mind…As mentioned above, Schrader cores have a tendency to leak. Before and after attaching your gauges to the chosen service fittings, check for leaks at each fitting, especially afterwards. Schrader cores can stick open unknowingly and allow refigerant to escape. Don’t be afraid to check compressor body welds and wiring ends of encapsulated pressure switches. Many have found leaks at these locations and will continue to do so. Refrigerant dye is also another option, some technicians stay away from it all together but it can be helpful as a last resort. Just use caution as it can create a mess.