It's a very common service call: A leaky system has lost refrigerant. Normally this problem is quite simple to diagnose. However, locating the source of the leak can be difficult.

Technicians can use several methods to find these leaks. Each method has its advantages and disadvantages. Some work well to locate a leak in one system but not as well in another.

A technician should know how to use more than one leak detection method. If one method isn't working, he can switch to an alternate one. Sometimes it is even beneficial to employ two methods while searching for a leak: one to locate the general area of the suspected leak and the other to pinpoint it.

Leak Detection Methods

Here are various ways to search for a refrigerant leak:

  • Visual inspection - As refrigerant leaks from a system, so does a portion of the refrigeration oil. The oil normally stains the area surrounding the leak's location. An easy way to search for a leak is to visually inspect lines and fittings for signs of oil. It may not pinpoint the location, but it gives you the general area.

    This method works well in those cases where a technician can visually inspect all of the piping with ease. This is not always possible. Often it is very difficult, or even impossible, to visually inspect all areas of a system.

  • Soap bubbles - Using an approved soapy solution is a very common method of locating leaks. Saturate the suspected area with the soapy solution. If a leak is present, the solution will bubble. This method works well if the area of the leak is known and if the system is adequately pressurized. It also works well in conjunction with other methods to verify the leak's location.

    It is normally best to use a soapy solution purchased from a supply house. However, some technicians make their own solutions. Homemade solutions work well as long as they do not corrode or freeze onto the tubing or fittings.

  • Electronic leak detectors - Most currently produced electronic leak detectors do an adequate job of locating leaks. A technician should always verify the operation of an electronic leak detector before relying on it. The sensors on most detectors need to be changed after a period of usage. Test their operation periodically to make sure you are not wasting time searching for a leak with a faulty detector.

  • Refrigerant dyes - Refrigerant leaks can be identified by injecting certain dyes into the system. The dye mixes with the refrigerant oil, and the point where this mixture leaks from the system becomes stained with dye. You locate the leak by looking for the stained area. Two basic types currently used are red and fluorescent dye.

  • Ultrasonic detectors - As refrigerant escapes from a system, it generates sound at a higher-than-normal frequency. An ultrasonic leak detector can pick up these sound waves. This method works well as long as no other sources within the system area produce sound waves at the same frequency.

    There is one basic rule you must follow while searching for a leak: have patience. At times, this process can be a very tedious and frustrating procedure. A little patience goes a long way.

    Joe Marchese is owner of Coldtronics, Pittsburgh. He can be reached at 412-734-4433,, or

    Publication date: 12/06/2004