In many of my blog posts, I go into lots of detail. For this post, however, I’m trying a shorter format for two reasons: a – our readers are busy, and want useful information in bite-sized pieces; and 2- the causes of leaks in AC evaporator coils seems more varied than the solution.
Symptoms of leak in indoor coils
- Periodically being told that refrigerant needs to be added
- AC system and fan runs, but warm air comes from vents
Causes of leaks in evaporator coils
In the HVAC forums I monitor, the posts on leaky indoor coils tend to come in waves, sometime focused in certain geographical areas. Humid climates tend to increase some of the issues. Lately the number of posts has been high. Leaky coil issues are fairly widespread, and are not limited to any particular brand. Listed below are some of the possible causes of leaks:
- Corrosion of tubes (“formicary corrosion”) increasing due to “tighter” house construction. Corrosion causes pinholes in the copper tubes
- Corrosive gasses or fumes from defective drywall or other building materials, contents, or household chemicals.
- AC coils being made of thinner-walled, lighter gauge copper
- Higher operating pressures in newer equipment
- Manufacturing defects in tubing
Possible solutions and questions to ask your contractor
- If your AC and heating system is older (10 years is a benchmark used by some of the municipal rebate programs) or not very efficient, before doing a major repair, such as replacing a compressor, coil, or heat exchanger, you should also compare the cost of replacement. Most rebates and tax credits require the installation of a new system to qualify. Plus you’ll lower your monthly utility bills and future repair bills. If you are in a position to possibly replace your system, you can use our free grid to compare bids.
- If your AC and heating system is otherwise OK, ask your HVAC contractor if either a plated (tin) or aluminum corrosion-resistant replacement coil will work in your equipment and situation. If you don’t have a reliable service company, you can visit this page to learn how.
If you have experience with a leaky AC coils, either as an owner or technician, please enter your comments so others can learn.