Air handler freezing

[ageless]

18,000BTU dometic split system. I noted the air wasn't as cool as it has been so I sought out a cause. Nothing obvious at the condenser so moved onto the air handle where I found the first 4" or so of the lines going in frosted. I checked the filter, washed it despite looking pretty clean, removed the ducts which were clean and flowing freely, turned the unit to high fan and within 10 minutes it was thawed. Both drain pans are dry but I still blew out the lines and ran water through them to ensure patency. Turned the unit back on and raised the temp from 70 to 74, IFR temp gun shows 83 at the filter, 71 at the vent. Any ideas where to go next, I'm thinking the only other option could be a leak. Will update in a few hours what the handler status is

[Boatsb]

Low freon. Let it defrost then check pressure.

[ageless]

Six hours from my original post and the air temp at the filter is 73, at the vent 57, ambient air at thermostat 74.6, thermostat on 74. The lines aren’t frosted but the windows are, super confused now

[Reefgeorge]

A freezing evaporator coil is caused by insufficient refrigerant going through the evaporator coil and/or not enough heat removal (work) by the coil.

Low evaporator work:

Air flow-
Fan motor problems
Blower assembly dirty
Restricted duct
Dirty filter
Dirty evaporator fins

Sensible/latent heat removal-
Long system runtimes
Very low temp settings
Very low humidity

Low refrigerant through coil:

Restriction at the metering device
Low charge

[doc g]

and add to the above list , sticky reversing valve. I flip mine on heat and back to cool once a month or so . I have had two of those over the years ....Pat

[Reefgeorge]

and add to the above list , sticky reversing valve. I flip mine on heat and back to cool once a month or so . I have had two of those over the years ....Pat

I belive that my SMXII cycles the reversing valve at each compressor start to equalize the system but I don't know which of the older units do not do this and could then benfit from doc's suggestion.

Also, I failed to mention that low charge is most peoples assumption with most AC problems and is often but not always the case. Because this problem can be a restriction in the refrigerant circuit, never add gas without diagnostics with a set of gauges as suggested by Scott because more charge on a restricted system can end badly.

[ageless]

3.19 lb low on Freon fixed the freezing

what is everyone paying for Freon these days?

[Reefgeorge]

$15-20/lb

[Boatsb]

Local ac guys are charging $80-100 per pound at service calls.

[ageless]

I guess I should have specified, R22.....The 3.19 lb's cost me $239