Safety12 min · 3 steps

Find a refrigerant leak

Soap what you can see. Electronic for what you cannot. UV dye is a last, documented choice — not a first spray.

Before you start

A2L: sniff the work area for flammable vapor and kill ignition sources before you crack a joint.
Do not use a halide torch or any open-flame detector on A2L.
Recover before you cut. A ‘small’ liquid-line spray is frostbite and, on A2L, an ignition cloud.

1 Confirm it is actually a leak
Weigh / clock the history. Standing nitrogen test if you already recovered. A 3-ounce winter loss on a 6-lb 410A is not ‘just seasonal.’ Ice, oil spots, and a low-charge chart with high SH are the usual tell.
Expect: A reason to hunt — not a ritual sniff on every PM.
If it fails: If the weight is on the plate and SH/SC are on the chart, you do not have a leak call.
2 High-probability joints first
Schraders and caps, service-valve packing, braze joints you or the last tech made, reversing-valve sweat, indoor coil hairpins, the liquid-line drier, and the crimp on a factory process tube. Soap with the system at standing pressure or on a nitrogen charge. Electronic at the base of the cabinet and along the lines with a slow pass — HVACR School: do not wave it like a wand.
Expect: A repeatable hit you can soap.
If it fails: No hit at the outdoor → indoor coil, evap hairpins, and the flare nuts on a ductless. Pull the indoor coil if the nitrogen test fails and the outdoor is dry.
3 Repair, test, evacuate, weigh back in
Recover. Repair (braze with nitrogen, or replace the core / valve). Nitrogen standing test. Vacuum with decay. Weigh in the nameplate charge — do not top off a leak. Replace the drier on an opened 410A / A2L POE system.
Expect: Standing test holds. Decay holds. Nameplate weight back in.
If it fails: A second loss next week is the joint you did not see — usually the indoor coil or a cracked vibration loop.

Dye contaminates POE and some electronic detectors. If you use it, write it on the ticket.
A leaking schrader is a 4-minute fix that gets skipped when someone is hunting a coil.

Practice distilled from public HVACR School and AC Service Tech material. OEM I/O and EPA 608 still win.