Hot answers tagged hvac
The Tee was left open as a means of a clean out. Start by using a shop-vac on that Tee and hold your finger over the other end, in the pump (you may have to get the pump out of the way). Next, snake it out, going into the machine: (e.g., the brush that comes with an EZ-Trap; johnstonesupply.com) Followed with another vacuuming. Ideally the first go ...
Unless you are an abnormally equipped layman, no. Even then, there may be a legal requirement (depending where you are) for this to be done by a licensed A/C service person, as regulations around refrigerants have become much more stringent over the years, trying to limit uncontrolled releases to atmosphere.
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