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Note: This project requires intermediate to advanced air-conditioning repair skills. Also, check with the manufacturer of the unit regarding detailed repair and warranty information.
Shut down the A/C unit outside and retract the coolant in the refrigerant line to avoid any spills. Only then can the refrigerant line be detached inside. Also disconnect the condensation drain line at the air handler.
Turn the power off at the electrical panel and disconnect the electrical at the air handler. Next, remove the fan system (also known as the squirrel cage) and remove the coil. Lastly, remove the air handler casing.
Begin cleaning the air handler by first vacuuming away dirt caked on the inside of the air handler casing.
To clean the coils, use an antimicrobial solution. When the solution turns the coils white, thoroughly rinse them with a garden hose. Follow the same procedure to clean the fan system (squirrel cage).
The air handler can now be put back together. Cut new insulated duct board to size so it tucks in and fits snugly around all sides of the handler (Image 1). Tape all seams with aluminum tape and burnish with a plastic rib. Paint on a coat of mastic adhesive cement to further seal each seam (Image 2).
Replace panels back onto air handler. Reattach coils and squirrel cage. Reattach the refrigerant line as well as the condensation drain line at the air handler.
Replace the old filter with a new heavy-duty filter (Image 3).
Note: Filters should be changed approximately once a year. If you have pets or allergies, change the filter every six months to ensure a fresh system.
As a final step, install new ductwork in the attic above the air handler, using plastic ties to hold the work in place, ensuring attic air won’t be able to get in from above.