My box is closed up tight and getting hotter

June 7, 2011 5:02 AM

How can I access and clean the evaporator coil in our air conditioner?

The air conditioner evaporator coil box sits on top of the furnace and appears to simply be a sheet metal box with no obvious access panel or doors. The house was built in 1989 so I'm sure the AC unit is from the same year. Is this typical? Am I going to have to cut into the box or is this unnecessary? Was my unit simply not intended for this type of service? I can possibly provide pictures or model information if necessary.
Thanks!

posted by mcarthey to Home & Garden (2 answers total)

Best answer: I've seen a number of residential AC units where the coil is not provided with an access door. Lazy/cheap installers. Be careful when cutting, you don't want to pop a line. The coil(s) will likely be installed on an angle or V shape inside the plenum

What you need to get is a fin comb. Run the fan for a while so the coil dries out, and then you pick the side of the fin comb with the same pitch as the spaces between the fins, and carefully insert comb into the fins and draw across. That will get out the majority of the built up gunk.

Then you squirt some cleaner that is safe for the aluminum (and possibly copper), let it soak in, and then rinse it carefully. In a perfect world, you do this from the reverse, against the normal air flow so that any gunk that is stuck in there will go out the way it came in. And you should do it gently so the dirty water goes down the condensate tube.

If the AC coil is on top of the furnace/blower area, you want to be careful not to get that part wet.

When you seal the opening back up, seal it well. Either caulk it, or get some of that foam in the "window screen and foam" aisle of the hardware store and stick it on so it seals up. Truck bed cap sealer strips seemed to work well for my last project.

And then make sure you use a better filter so you don't have to do this again.
posted by gjc at 5:44 AM on June 7, 2011

Response by poster: Thanks for the reply. I was hoping for something magical but I'm afraid it's either the coil or I'm simply low on freon due to a leak. The AC unit is 13-14 years old and I'm trying to put off a replacement. I have been trying to determine if the condensate tube is plugged since after it freezes up the water tends to run out all over the place but this could be due to the volume of melting ice. I'm still working to determine the exact cause.
Thanks
posted by mcarthey at 8:04 AM on June 7, 2011