Finding Freon Leaks

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Finding Freon Leaks

Author: Bud Chick

The shot below is of an up flow air conditioning evaporator coil as typically found on top of a gas furnace. Your coil may be housed in it's own metal cabinet called a "Cased Coil" or you may have a coil set inside of a metal or fiberboard supply plenum. To find the coil you will need to remove the cabinet screws if it is a cased coil or you may have to cut into the plenum with sheet metal cutters in some cases. Please be fore warned that if cutting into a sheet metal plenum extreme care must be used so as NOT to cut into any refrigerant copper lines as there is usually extremely high freon pressures in these lines. If you are going to attempt this always wear protective eye wear and gloves as freon in the eye will "Burn" the eye PERMANENTLY! Many have the misconception that freon "Freezes". The exact opposite is true. If you let freon out on the ground (a E.P.A. violation) it would "boil" even at a temperature of about 40 below zero! If unsure of yourself, please call a qualified HVAC Company to do this work.

Checking for freon leaks means being sure there is some freon in the system or you will have no pressure to complete the check. This evolves painting a strong non alkaline solution made for this purpose (don't use household products as they are corrosive eventually) on any and all joints of copper, fittings, capillary tubes, tubing bends, metering devices or T.X.V. (Thermal Expansion Valve), strainers, filters, dryers or any other connections. The refrigerant lines that run from the evaporator coil to the outdoor unit are "checked" in the same manner. To see this Leak Solution and a kit to fix leaks on the service valves click here Freon Leak Kit

An even more accurate way of finding virtually leaks as small as 1/2 an ounce a year is to use a Leak Detector meant for the pros here Freon Electronic Leak Detector (You can see the Electronic Leak Detector being used below on an out door condenser coil.)

Below, note the small capillary tubes that are protected with a black piece of refrigerant line set insulation. Vibration over the years often make leaks at these tubes - if they are leaking a VERY skilled service technician MAY be able to seal the leak but usually it is time for a new coil.

All the tube bends at BOTH ends of the coil need to be "checked" (if you can get to them). The metering device or TXV also need to be "checked". If using the leak solution, paint it on liberally and watch VERY closely for any bubbles no matter how tiny they may be. If there is a bubble, that is a leak. This is where the Electronic Leak Detector saves a lot of time and is much more sensitive in finding leaks. It's only draw back is when being used out side on a windy day, the wind will sometimes blow the freon AWAY from the detector so it is best used on quiet days. In short, if there is a copper connection, test it! This is a VERY time consuming process.

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Below is a T.X.V. (Thermal Expansion Valve). It may be used in place of a fixed metering device and may be mounted within a cased coil or externally mounted on the large suction refrigerant line. TXV's are much more accurate in metering refrigerant and are usually found on the higher end AC units. They are sometimes found also on the out door section of Heat Pump split systems and all in one package heating and cooling units.

Thermal Expansion Valve

Below we are leak checking the liquid line service cap. These caps actually have to be removed to test it (picture is only for reference).

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Below is a liquid line filter dryer as found in the small refrigerant line. This particular unit uses an internally mounted filter dryer so we are only showing this for reference. You may also have a suction line filter dryer mounted in the large copper line. Paint all these joints or use an Electronic Leak Detector.

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The shot below is looking down through the fan section to see the out door coil (condenser coil). You will also have to disassemble the outdoor cabinet to get to all the tube bends just as as indicated on the indoor evaporator coil. Note the copper to aluminum joints? They are joined at the factory using a special process and seldom leak on a Trane unit however other brands don't have such a good failure rate so check these joints too. The compressor should be "checked" itself including the welded "can" of the compressor.

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In summary, finding freon leaks is a very time consuming job and requires patience on the testers part. By taking your time however you should be able to find all of your leaks.

Some of the questions we get asked are below.

How long should freon last?
Answer: In theory - forever. But in practice, if the unit was installed correctly it should go 10 years before common leaks may show up.

Can I install freon myself?
Answer: No. It takes special equipment used under pressure to install. It also requires knowledge of HVAC to do as well as an E.P.A. License to buy and use freon.

Can I buy Leak Stop kits as are available for cars?
Answer: No. Any car product put into your central home system will plug all sorts of things up, void warrantees and cost you a fortune to repair! Don't even think about it! Once your leaks are fixed and your unit properly charged you may want to look at this kit Freon Leak Kit

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