A refrigerator uses refrigerant evaporation to cool air blown across an evaporator coil. A compressor pulls the refrigerant vapour back and condenses it to a high-pressure high-temperature vapour. This vapour cools and condenses back to a liquid as it passes through a fan cooled condensing coil. Then high pressure liquid travels back to an orifice at the start of the evaporator coil where the process starts over. Residential refrigerators should have the freezer set at -17.8 degrees Celsius and the refrigerator set at 2.78 degrees Celsius.
Remove the panel covering the evaporator coil. This panel, found in the freezer compartment, will need either a Phillips screwdriver or a 1/4-inch nut driver to remove the holding screws.
Remove the hold-down clamps on the evaporator coil with either a Phillips screwdriver or a 1/4-inch nut driver. Hold-down clamps prevent the coil from vibrating when the refrigerator runs and screw directly to the refrigerator body.
Find the leaks in the evaporator coil. Look for rubbed areas, oily spots and heavily oxidised areas. Pay extra attention to the bends in the coil tubing.
Clean the leak area with sand paper. Completely remove all loose material and debris, especially refrigerant oil. Avoid pushing debris into the hole. Wipe all sanding dust off of the leak area with a clean rag.
Connect a vacuum pump to the refrigerator's refrigerant service valve, found near the compressor. The service valve looks like a oversized valve found on a tire, except its made of metal. A hand-held automotive vacuum pump will work on a refrigerator.
Pull a vacuum with the vacuum pump. Try to create a vacuum of at least 10 inches of mercury. Large leaks in the evaporator coil may prevent this. A vacuum will pull the patch into the leak, creating a better bond.
Knead a 1 inch section of epoxy putty with your hands. Continue to mix the putty until it has a uniform colour and texture.
Press the epoxy putty over the leaking area. Wrap the putty around the pipe. The patch should extend about 1/2-inch on each side of the leak. Finish applying the epoxy putty within 3 minutes of mixing.
Check the vacuum gauge. Pull a 10 inches of mercury vacuum on the refrigerant system. Disconnect the vacuum pump.
Check the vacuum reading after 24 hours. A leak still exists if the vacuum reading has dropped. Perform a leak test and repair as necessary.
Moving the copper defrost bulb away from the bends on the evaporator coil will often reveal hard to find leaks.
Do not attempt to solder a refrigerator's evaporator coil. The aluminium coil has thin walls and will melt with extreme heat.