Replace a Schrader (Access-Valve) Core

Replace a leaking Schrader/access-valve core UNDER PRESSURE with a core-removal/installation tool (no full recovery needed), seat/torque the new core, fit a sealing cap, and leak-check — the cheap fix before assuming a system leak.

Approx. 25 min

Before you start

•Leak isolated to the Schrader core itself: bubbles or a detector hit AT the service port that stop when a known-good cap is snugged, while the rest of the system holds.
•A valve-core removal/installation tool on hand (lets you change the core under pressure without recovering the charge), plus replacement cores rated for the refrigerant/pressure.
•Eye protection on; system is charged (this is done live under pressure).

Tools & materials

Valve-core removal/installation tool · Replacement Schrader cores (refrigerant-rated) · Leak-detect solution or electronic leak detector · Sealing service caps (with gasket/O-ring) · Safety glasses

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Confirm the core is the leak

Confirm the leak is the core, not the port body
Bubble or sniff the open service port: a leak that's at the core (stops with a good sealing cap, no leak around the port threads) is a core swap. A leak around the brazed port body is a different repair.
Tools: Leak detector
Target: Leak at the core only; port body/threads tight
Glasses on — this is done under pressure
You're changing the core with refrigerant pressure behind it. Wear eye protection and keep the port pointed away from you and others as the old core releases.
⚠ Done under refrigerant pressure — wear eye protection and keep the port aimed away; refrigerant can frostbite skin/eyes.

Swap the core with the tool

Remove and install the core under pressure
Thread the valve-core tool onto the port, close its internal valve, engage and back out the old leaking core into the tool body, then push the new core in and thread it down — all without venting the system. The tool's seal holds the charge while the core is out.
Tools: Valve-core tool, Replacement core
Target: Charge retained via the core tool; no recovery/evacuation needed
Seat and torque the new core
Seat the new core firmly so it doesn't leak past its seal, but don't overtighten and strip/crush it. Back the tool's valve open and remove the tool.
Target: Core seated firm, not over-torqued; tool removed cleanly

Cap & leak-check

Fit a sealing cap and leak-check
Install a sealing service cap (with its gasket/O-ring) finger-tight-plus — the cap is the second line of defense against a port leak. Bubble or sniff the port and cap to confirm no leak remains.
Tools: Sealing service cap, Leak detector
Target: Sealing cap fitted; no bubbles/detector hit at the port or cap