Install a Filter-Drier

Orient the arrow toward the metering device, braze with a nitrogen purge while heat-sinking the core, then pull a proper vacuum — and always fit a new drier when the system is opened.

Approx. 60 min

Before you start

•System recovered (or pumped down/isolated per the job) so the liquid line can be opened safely — never braze on a charged/pressurized system.
•Correct drier on the truck: matched to refrigerant, tonnage/flow, and connection (sweat vs flare) — a NEW drier, since the desiccant is hygroscopic and a used one is spent.
•Nitrogen with a regulator set for a low purge flow, and a wet rag / heat-sink paste to protect the drier core.

Tools & materials

Brazing torch + rod (e.g. 15% sil-fos for copper-to-copper, brazing flux if to brass/steel) · Tube cutter + deburring tool · Nitrogen + regulator (for the brazing purge) · Wet rag / heat-sink compound · Vacuum pump + micron gauge

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Locate & orient

Install with the flow-direction arrow toward the metering device
Cut the drier into the LIQUID line and point the stamped flow arrow in the direction of flow — toward the metering device (TXV/piston). Backwards, the drier won't filter/dry properly and can dump trapped debris into the valve.
Target: Arrow points downstream toward the TXV/piston; drier sized to system tonnage and refrigerant

Braze it in

Braze with a flowing nitrogen purge
Trickle dry nitrogen through the line while brazing so you don't form copper-oxide scale inside the tubing. That black flaky scale breaks loose and plugs the metering device and clogs the very drier you're installing.
Tools: Nitrogen + regulator, Brazing torch
Target: Low, steady N2 purge (~2–5 SCFH) flowing through the joint during all brazing/cooldown
⚠ Purge through an open end — never trap nitrogen between two closed points while heating (pressure/explosion risk). Keep a fire watch.
Heat-sink the drier core
Wrap the drier body with a wet rag or apply heat-sink compound and keep the flame on the joint, not the can. Overheating cooks the desiccant core and can crack it — protecting it keeps the new drier actually working.
Target: Keep the drier body cool (wet rag/heat-sink paste); braze the joint without baking the can

Evacuate & restore

Pull a proper vacuum after brazing
Pressure/leak-test, then evacuate the opened section to a deep vacuum and run a decay test before restoring the charge — opening the line let in air and moisture that the drier alone shouldn't have to swallow.
Tools: Vacuum pump, Micron gauge
Target: Evacuate ≤ 500 microns and hold on a decay test before restoring/topping the charge
Always replace the drier when the system is opened
Any time the sealed system is opened (compressor change, leak repair, line work), fit a fresh drier. The old desiccant has already adsorbed moisture/acid and offers little further protection.
Target: New drier every time the refrigerant circuit is opened