My question is how I get to the A-coil to clean it. This particular furnace has a lousy filter setup, which allows dust to get around it. I know the coil is dirty, because the blower has a lot of dust in it. I am also hearing a whistling around the top of the furnace when the blower is on, so I'm thinking there is a lot of resistance to air flow. There is a cover on the top of the furnace to access the coil, but I don't know how to proceed from there. I want to blow out, or vacuum the coils and use a cleaner on them to get the most out of heat transfer. I also know that it's very important not to bend the fins or bend the freon lines. Is there a way to slide the coil out? Thanks all. Bill

Well, that was interesting. I took the top furnace panel off, and the A-coil had a plate on the end. Sitting in front of the plate was a live brown cricket and a petrified mouse. (How did they get there?) You have to remove that plate to get to the underside of the coils, but Carrier didn't design it with the service man in mind. Because there are cooling lines running across the bottom, you can't get the end plate off without cutting it in half. Brilliant design ! After cutting it in half I got it off and the coils were fairly dirty. I took a towel and set it across the heat exchanger below and carefully brushed off the excess dust (running parallel with the fins, so you don't bend them) and vacuumed them with a brush as well. The a-coil is narrow, so it's not easy working inside it, and it would have worked better if I had a compressor to use compressed air and blow the coils out from above (opposite of the normal air flow direction). I'm not sure, but I think that would get them cleaner. Then I took a can of spray cleaner (you don't have to rinse it off, the condensate with do that) and I sprayed the foam on the bottom side of the coils until the can was empty. That too is easier said than done. After cleaning the coils as well as I could, I put the two sections of end plate back on (after hammering the edges that I cut to flatten them), and I cut an additional two inch piece of galvanized metal to cover the cut I made, and screwed it on as well. I don't know how much a serviceman charges to do this cleaning, and I wonder how good of a job they could do. It is much better to make sure that dirt doesn't get past the furnace filter, because once it does, it gets blown out of the blower and up into your coil. My filter has no flanges around the top, bottom, and back, where it goes in to the furnace. All it has holding it is a piece of wire going across the middle of it. When the blower is running, there is nothing to stop the edges of the filter from lifting away, and letting dirt go around it. It is another very poor design in a furnace that wasn't cheap. Looking back, I should have complained to carrier, or had the installer install flanges around three sides of it. If you are buying a new furnace, check to see that it has a filter slot that won't let the filter lift away around the edges, because, what also happens is that if the filter gets too dirty it will literally crease along the wire and try to fold in half. That lets all the return air go around the filter, which I learned the hard way. I then had to pull the blower assembly out and clean it. I now use a rigid washable filter with a plastic frame, and I clean it every few months. Anyway, I thought I would post this for anyone who might be thinking about doing this. Bill

Now that I have cleaned the A-coil I have had the condensate line clog up twice. When this happens, water runs down inside the furnace, on the burners into the blower compartment, etc. I pulled the tubing off the drain and slid a piece of plastic yard trimmer line into the hole, and out came a ton of water. I suspect that cleaning the coils has caused a lot of dirt to drain off the coils. There is a threaded black plastic tubing connector on the furnace where the condensate drains. Can I unscrew that so I will have a larger opening to maybe run something in there to get some of the dirt, or is this more likely a algae, or other gook that's causing this? Thanks, Bill

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It's all gook, no matter the type.

You can unscrew the fitting, but I don't expect the hole
is gonna be much bigger than the tubing....

anything will help.

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Ok, thanks.

I'll keep an eye on it for more backups. I guess the gook is a sign that I did get some dirt out of the coils. I'm glad I cleaned the units, evaporator and compressor, because they were dirty, and with our ten days of over 100 deg. it had to help. You can relate to that, where you live. Thanks.