AC Evap Coil Freezing

[TheGuy]

So, as we came into the warmer months I noticed the AC seemed to be struggling. After our first trip, it seemed like it never turned off. As a result, I took a look through the plenum and saw it was freezing up. That weekend, I got up there and cleaned out the coils. The evaporator was pretty dirty, but not bad enough to significantly impede airflow in my opinion. That didn't help. Before I replace this thing, I thought I'd throw a thread up and see if anyone had additional ideas.

Here's the list of symptoms and checks I've made:

Symptoms:

1. Poor Cooling Performance
2. Evaporator Icing only Halfway
3. Compressor Not Cycling (or Very Rarely)

Observations/Checks:

1. Airflow at vents seems normal
2. Output plenum is properly sealed from the return air.
3. Evap and Condenser Coils are Clean
4. Thermal Probe is in Place
5. Evap coil ices top-down to probe; air comes out cooler than ambient, but not sufficient to cool the space.
6. No signs of kinks in the capillary tube
7. No oily leak that I can see (like I'm accustomed to with cars)

Since these units are meant to be disposable (disgusting, given their cost) I have to replace it. The dealer says they'll be happy to do it for me... In July. Well, I'm using this as my WFH office for the time-being and we won't last to July. So, this is at least somewhat urgent to fix.

Anything else I can check before I bite the bullet and order a $1500 replacement for my not 4 year-old AC?

[BobLandry]

If you do not see evidence of an oil leak, the unit is probably charged correctly. These units are charged and sealed at the factory. Occasional one slips away from the factory with an incorrect charge, but their manufacturing processes are pretty tightly controlled and it doesn't happen often. I know this as a Dometic marine dealer. If the icing were caused by airflow, the entire evaporator would be freezing. Your description is one of a starved evaporator.
My educated guess is that there is a blockage or partial blockage in the capillary system. These are small tubes that meter the refrigerant to the evaporator. It could be clogged by junk that was introduced at manufacturing. It happens. The cost to have the cap tub(s) and strainer replaced would probably be cost prohibitive.
You can find the units online for $700-800 and they are not that difficult to replace.

[TheGuy]

Forgot to post the pictures...

Iced up evaporator


Side of compressor; That's the only bit of rust I see aside from bolts.


Some sort of dried-up residue on the bottom. I'm not sure what that is, but it looks like it came from the hole where the pipes go through the bulkhead to the evaporator core.


Another shot of that...

[TheGuy]

If you do not see evidence of an oil leak, the unit is probably charged correctly. These units are charged and sealed at the factory. Occasional one slips away from the factory with an incorrect charge, but their manufacturing processes are pretty tightly controlled and it doesn't happen often. I know this as a Dometic marine dealer. If the icing were caused by airflow, the entire evaporator would be freezing. Your description is one of a starved evaporator.
My educated guess is that there is a blockage or partial blockage in the capillary system. These are small tubes that meter the refrigerant to the evaporator. It could be clogged by junk that was introduced at manufacturing. It happens. The cost to have the cap tub(s) and strainer replaced would probably be cost prohibitive.
You can find the units online for $700-800 and they are not that difficult to replace.

Someone on FB suggested a similar diagnosis. I wonder how that just became an issue after several years of service.

[BobLandry]

Bits of debris can be picked up during manufacturing. Sometimes it never shows up, sometimes it does. Luck of the draw.
If you have a buddy that does air conditioning, the parts to fix it would probably run $30.

[BobLandry]

Can not see your attachments.

[TheGuy]

Can not see your attachments.

Weird... I added them again and now they show up. Go figure.

[BobLandry]

I don't see anything unusual in the photos. Remember, you're dealing with painted steel parts that are basically exposed to the environment, and cheap paint at that.

[TheGuy]

I didn't see anything either which is what bothers me.

[BobLandry]

Don't let it. If nothing seems awry, everything externally is OK. I think you have an internal refrigerant blockage.