Sanyo 12k mini-split freezing up

[CJCar]

Hey all, I need help diagnosing an older Sanyo mini-split. It's a 12k single head unit. Ran fine this past fall and spring for heat (pellet stove over winter). The unit blows cold air and will maintain 74 degrees, but if we set the t-stat below 74 the unit will freeze up. Frost starts at the line set at the condensing unit and eventually the evaporator coil will frost over. Filter screen on the indoor unit is clean, both condenser and evap coils appear to be clean. It's been mid to upper 80's with 60-80% humidity here.

Am I looking at a low charge or possible air flow issues? I have not hooked up gauges or pulled the blower wheel to inspect since we've been here (4 years).

Thanks!

 

[American Locomotive]

If the frost starts at the lineset, it's not a low air flow issue. Either the expansion valve (EEV/EXV) inside the unit is stuck or restricted, or the charge is low.

Usually on a minisplit its not a good idea to just add gas. Usually you'd **** out the existing charge and weigh in a new charge.

Probably a small leak at a flare fitting.

 

[metlmunchr]

To check for leaks at flare fittings, you can put it in heat mode which will greatly increase the pressure on the line set and fittings. If it's an inverter unit, crank the t'stat up and wait a few minutes for the unit to ramp up to full output. You'd then typically have 350psi or more on the lines (assuming it's a 410a unit) which makes it much easier to detect a leak.