AC - frozen tubes, no air flowing when fan on and system off

Question

Last night I realized my AC stopped working. I turned the thermostat to 74 degrees and by the time I woke up the house temperature was 80 degrees. My home has a single Carrier compressor (obviously outside). The air handler, evaporator coil and blower are upstairs in the attic.

I spent the day troubleshooting and figured out a few things:

• The refrigerant-filled tubes that come out of the compressor unit and into the house had ice around them, but right outside the compressor case and right before entering the house (see 2 pictures below).
• The condenser seems to be working OK as I can see some water on it (see picture).
• On the thermostat, when the system is off and the fan is on no air comes out of the registers (is my blower broken?). Every 5 minutes the attic makes a loud noise for about 10 seconds, a motor noise. I could smell burnt in my bedroom for a few minutes as well.
• Return vent filters were replaced 3 weeks ago.
• I cannot open the evaporator coils as the casing seems to be "glued" somehow with sparkling (??) or some sort of tape (see picture with red arrows).
• There is a tube coming out of the furnace in the attic with some green liquid spill around it. I'm assuming it's the refrigerant liquid. Is this normal or is there a leak going on?
• After speaking to an AC repair guy over the phone, he thinks the blower is broken. That makes sense and would explain the loud noise (blower trying to work) + the "burnt" smell + the fact that there is no air coming out of the registers even when the fan is set to "On" on the thermostat.

Any thoughts will be much appreciated.

Answer 1

The AC coil in your ductwork is freezing due to insufficient airflow across the coil. The coil needs to transfer heat by having airflow across it. If there is no airflow the coil freezes; hence, the ice. The coil is either too dirty for sufficient air to pass through or the fan blowing air isn't working anymore.

Thanks, Tom

Answer 2

I think Ed's answer is on point, in fact from your story I don't assume the fan is bad. I think he is spot on, its thermal overload. So, the fan COULD have, or WILL burn out, so, turn the system off. Open all of the registers, let the hot air in. It will need to thaw (almost certainly!)

With all that said, I'm also in agreement that the green liquid is likely algae . This makes me actually wonder more if your condensate drain line is plugged AND also if the pump itself is burned out. They are "cheap" and the float limit switches, and the motors, and the pumps, that make up these units are not very expensive. I'd almost say that if you can move that drain line by hand to a bucket, go for it. You want to get that water out of the unit.

Also the core issue could have been from condensate not getting out of the unit. Again to Ed's point, you may have a 40lb block of ice in there. The air cannot get past it, the motor shuts off. after a few hours, you can try having a helper call for fan, and feel the plenum, if it starts vibrating, your motor "works" - turn it off and wait until the water is done draining from the unit. It might take a day!

You'll probably want to get the coils cleaned, if there is algae at the outlet, there is probably in the unit. It also could have been blocking air flow, promoting ice build up, and maybe helping you get unpleasant smells from the unit.

Having an AC tech there, they will pressure test almost always as a matter of procedure, so they will rule out leaks quickly.

Answer 3

Turn the system off and let it warm up this may take a while if the evaporator coil is frozen up. When a system charge is low icing of the coils is a indication. The fan motor may be bad but once fully defrosted it is possible it will work. (Thermal overload tripped and was just hot because the coils were iced up) . If you can not get into the evaporator coil the indoor one give it a good long time to thaw out there may be 20-40 pounds of ice in there and it takes a while. The green liquid could possibly be a leak we regularly narrow leaks down by spotting oil that has leaked. The green liquid could be condensate that has grown some green gunkies. Don't jump to conclusions I have seen systems do exactly what yours has done that worked after thawing. In these cases adding some Freon or in more severe cases pulling the system to a vacuum after repairing the leak and recharging has worked for me. The noise every 10 minutes may be the thermal overload on the fan resetting and then overheating from blocked coils. I did not see the photos on first review but the PVC line looks like your condensate line and it has been leaking could be plugged with algae or my technical term Green Gunkies. The coil and drain need to be cleaned for health reasons! The heavy frost could be from a low Freon charge or the evaporator coil icing up and the heat exchange not occurring. Since you can not open the evaporator get an HVAC person to do it it was probably sealed with calking that a razor knife can cut through the system must be opened and inspected at a minimum.