When it comes to the parts of your standard air conditioning unit, few are quite as essential as the condensing or evaporating coil. This coil is filled with refrigerant that draws heat out of the air passing over it. The coil is basically responsible for the entire cooling effect, with the rest of the equipment handling the work of moving the air around or switching the system on and off. A leak in the coil allows refrigerant to escape and causes a lack of cooling. Before you use a coil sealant product you've found online for a DIY repair, find out if they really work or not.
Complexity of Coil Leaks
Before you assume you can simply apply sealant to one spot and enjoy your normal cooling performance again, consider the length and size of the coil. Most coils start leaking due to corrosion since they're regularly exposed to many chemicals and moisture. If there's one visible spot of rust or corrosion, it is almost guaranteed that there is more corrosion spread widely over the length of the coil. Trying to seal dozens of leaks, most of which will be too small to see, will take hours of work with little payoff.
Chance for Serious Blockage
While some coil sealants are soldered or spread onto the outside of the coil by hand, most are designed for injection into the entire coil and claim to find and fill in leaks wherever they exist. Unfortunately, injecting anything other than approved refrigerants into the coil will likely cause a complete or partial blockage somewhere. These blockages cause your air conditioner to run even more poorly and increase the cost of repairs. You may even need a whole new air conditioner instead of just a new coil if the blockage causes the unit to overheat.
Continued Lack of Refrigerant
Using a sealant product also does nothing to replace the refrigerant that was lost through the leaks in the coil. Even if the system is completely sealed against just by the use of a sealant product, it will still fail to produce enough cooling power. Running the air conditioner with a low level of pressure in the coil causes strain on every part of the system, increasing the chances of a different kind of breakdown. Many HVAC contractors will only add refrigerant to a coil that they've inspected and repaired themselves, and will not add refrigerant if they find evidence of sealant use since a blockage in the coil could cause the refrigerant to blow out during pressurization.
Contact a service, like Air Around The Clock, for more help.