Leak_DetectorEvery air conditioning system leaks whether it is one ounce per year or one ounce every thousand years. The leaks are caused by cracks, bubbles, impurities, and other flaws in the brazing, joining, or manufacturing process. While they may not be detectable, they are leaks nonetheless and will eventually become detectable given enough time. The pressure, heat, and vibration from normal day-to-day operation is what causes them to become a problem.

If you are new to the HVAC field, here are some quick and  basic leak detection procedures to help you locate the source of the leak.

Oil Spotting

When there is a leak, the refrigerant blows out of the hole. Often it will blow the refrigerant oil out with it, marking the general area of the leak. Look for a wet spot covered with a very fine coating of dust or dirt. With your finger, check to make sure it is oil and not moisture caused by condensation. To pinpoint the location of the leak:

  • Ensure the power is disabled from the unit and and the pressure in the system is equalized.
  • Spray the general area around the oil with a leak detection solution. Do not use a homemade soap solution.
  • Look for foam or bubbles. If the leak is small, it can take 10 to 15 minutes for them to appear.

Oil spotting is great way to quickly check for leaks but is not always accurate. Oil is not present at every leak and if there is oil present, it could be from motors, pumps, previous leaks, or from removing refrigerant hoses.

Electronic Leak Detection

Whether you are testing the evaporator coil or the condensing coil for leaks, these basic steps and procedures are the same:

  1. Safety. Make sure all power is disabled to the system.
  2. Calibrate and set your electronic leak detector to its highest setting.
  3. Sniff for 10 minutes.
  4. Recalibrate your detector between tests.
  5. Two positive hits, indicate a leak.
  6. Two negative hits, rules out detectable leaks.

Condenser Coil Leak Search

Use a tarp and cover the condensing unit completely. This prevents the wind from blowing the refrigerant away from the source of the leak and concentrates the refrigerant for easier detection. Place your leak detector under the tarp and check for 10 minutes. Remember to check twice before making your determination.

Once you have determined there is a leak. Remove the tarp and begin to pinpoint the leak by using your leak detector and a leak detection solution.

Evaporator Coil Leak Search

Evaporator coils are more difficult to leak search because they are cased and difficult to access. However, like the condenser coil there is a quick way to determine if there is a leak in the evaporator coil.

Cut or locate an opening in the condensation drain that is below the coil. Place your leak detector into the drain pipe and monitor for 10 minutes. Since refrigerant is heavier than air, it will migrate down the pipe and the leak will be detected. Remember to check twice.

If an HVAC leak detection, then you can expose the coil to pinpoint the location of the leak.


There are other methods you can use to check for leaks and your ability to locate leaks will improve with time and experience. Note – It is never acceptable to just ‘top off’ or ‘gas and go’ when you suspect or find a leak in a refrigeration system.

Ron Walker
Ron Walker

After retiring from the U.S. Marines and achieving his B.S. degree, Ron Walker entered the HVAC field. He has been an HVAC technician, service manager, and business owner. Working as a service manager, he spent many years training HVAC technicians to be more technically competent and really understand their trade. His passion for teaching and helping others resulted in the creation of HVAC Training Solutions, LLC.