The first two articles settled "should you even add any." This one is the actual hands-on tutorial.
Read the safety incantation first, then continue.
🚨 Safety red lines (must read)
- R32 and R290 (propane) are flammable/combustible refrigerants. Near open flame or sparks they can ignite or explode. Non-professionals, or poorly ventilated enclosed spaces — don't do it yourself, call a tech.
- Work involves live equipment and high-pressure lines. Always power down before connecting gauges; wear eye protection and gloves.
- Before charging you MUST confirm: correct type, no leak (or leak already fixed), well-ventilated space, no open flame.
- Not sure? Stop and call a pro. Saving a few bucks isn't worth the safety risk.
1. Confirm three things first
- Refrigerant type: check the outdoor nameplate (R22 / R410A / R32), buy the matching refrigerant, never mix types.
- No leak: run the Sign-4 check from article 02; if there's oil residue, fix the leak first.
- Tools ready:
- AC manifold gauge set (blue/red/yellow hoses)
- Matching refrigerant cylinder (R22 or R410A / R32 specific)
- Charging hose + quick couplers
- Digital scale (for weight-based charging — advanced, more accurate)
- Soapy water (for leak testing)
- Eye protection, gloves
2. Procedure (the common "top-up" case)
Step 1: Safe environment and power-down prep Pick a well-ventilated day, cut power to the AC. No open flame or smoking near the outdoor unit.
Step 2: Connect the gauge
- Blue low-pressure hose → outdoor unit's thick-line (low-pressure) valve service port;
- Yellow hose → refrigerant cylinder;
- Red high-pressure hose left disconnected for now (a top-up only touches the low side; keep red closed or connect to a vacuum pump if needed).
- Tighten all fittings so they don't leak.
Step 3: Purge the air (critical!) Air and moisture inside the hoses will ice up the lines and wreck the compressor if they get in. To purge:
- Slightly loosen the yellow-hose-to-cylinder fitting, crack the cylinder valve just a touch, let the gas push the air out for 2–3 seconds, then tighten immediately.
- This is "chasing out air," not bleeding off refrigerant — don't open it wide.
Step 4: Run the unit at max cooling Power on, remote set to cool mode, lowest temp (16–18°C / 61–64°F), fan on high. The compressor has to be running hard so the low-side valve is in a chargeable state.
Step 5: Charge slowly
- Open the cylinder valve; refrigerant flows from the yellow hose through the gauge into the low side.
- R22: can be charged as vapor (cylinder upright), watching pressure as you go;
- R410A / R32: usually charged liquid by inverting the cylinder (faster, more accurate), but control the flow, don't dump it, and mind the flammable risk.
- Watch the gauge as you charge; stop near the ranges in article 02's table, and feel the thick line — when it's "ice-cold with beads of water" again, you're about there.
Step 6: Weight is steadier (recommended) If the nameplate lists a "charge amount (g)," weigh the cylinder on a digital scale and charge to that gram figure — more accurate than guessing by pressure.
Step 7: Leak-check and wrap up
- Close the cylinder valve, turn off the AC, disconnect the gauge (confirm valves are reset before disconnecting so gas doesn't spray on you);
- Brush soapy water on every joint; bubbles mean it's not tight — tighten;
- Run a 10-minute test: vent is bone-chilling, outdoor thick line has condensation. Done.
3. Common ways to mess it up
- Overcharged: pressure too high, compressor hits high-pressure cutoff, cools worse;
- Undercharged: same as not doing it, wasted effort;
- Mixed types: R22 and R410A / R32 must never mix — mixed, the compressor is toast;
- Skipped the air purge: air and moisture get in, ice blockage, corrosion;
- Added without fixing the leak: stressed already — fix the leak first.
Next up
Recharging feels simple once you know how, scary before you do. The next article is a pitfall checklist + the hard red lines for calling a pro, to help you decide "should I do this myself, or pay for peace of mind."
