Replace a Compressor (Condenser)

Before you start

•Compressor confirmed failed (no start with good cap/contactor/voltage, open/grounded windings, locked rotor, or mechanical/check-valve failure on a scroll) — not just a missing run component.
•EPA Section 608 certified; recovery machine + DOT cylinder on hand to recover the charge before opening anything.
•Correct replacement compressor: matched refrigerant, tonnage/BTU, voltage/phase, and the same start components (run cap, and start cap/relay or PTC if so equipped).
•Decide whether it was an electrical burnout (acid smell, blackened/burnt oil) — that changes the cleanup (mandatory suction-line drier, possibly a flush).

Tools & materials

Recovery machine + DOT-rated recovery cylinder + scale · Megohmmeter (insulation tester) + multimeter (ohms/continuity) · Brazing torch + rod/flux, nitrogen + regulator (flow purge) · Tube cutter (cut out, don't unbraze under pressure), deburring tool · Suction-line filter drier + new liquid-line filter drier · 2-stage vacuum pump + micron gauge, charging scale + refrigerant

0% complete

Confirm the failure & make safe

Lock out power and verify zero volts
Pull the disconnect, lock/tag the breaker, and verify 0 V at the contactor line side before touching anything. Discharge the run/start capacitor.
Tools: Multimeter
⚠ Lockout/tagout and verify 0 V with a meter — the compressor circuit and capacitor are lethal.
Megohm + ohm the windings; check for a burnout
Bleed the caps, then ohm Common-Run, Common-Start, and Run-Start (they should add up correctly) and megohm each terminal to the shell for insulation to ground. An open winding, a short, or a low megohm reading confirms an electrical failure. Smell the suction line / look at the oil — an acid smell or black, burnt oil means a BURNOUT, which dictates the cleanup.
Tools: Megohmmeter, Multimeter
Target: Windings not open/shorted; insulation-to-ground typically in the megohm range when healthy; acid smell / blackened oil = burnout
Recover the refrigerant before opening the system
Recover the full charge into a DOT cylinder per EPA 608. Do NOT unbraze or cut a system that is still under refrigerant pressure.
Tools: Recovery machine + cylinder + scale
⚠ Never apply a torch to a pressurized system — recover it down first. Venting is illegal.

Remove the old compressor

Photograph + label the electrical and tubing
Photo the terminal wiring (C/R/S, overload, start components) and the suction/discharge orientation before disturbing anything.
Cut the compressor out — don't unbraze it in place
Cut the suction and discharge lines with a tube cutter rather than unbrazing on the unit; this avoids dumping oxidized scale and residual oil into the system and avoids torching near a possibly oily compressor. Unbolt the mounting feet/grommets and lift it out.
Tools: Tube cutter
⚠ Leftover oil can flash — cut, don't torch, near the old compressor body.

Install the new compressor & driers

Set the new compressor on its grommets/feet
Mount it on fresh isolation grommets in the correct orientation, plug nothing yet, and leave the shipping plugs in until you're ready to braze so it doesn't pick up moisture.
Install a suction-line filter drier after a burnout (mandatory)
After ANY burnout, install a suction-line filter drier ahead of the compressor to capture the acid/contaminants the burnout left in the system, in addition to a new liquid-line drier. (On a clean mechanical failure, the suction drier is good practice and is often left in temporarily then removed once the system runs clean.)
Tools: Suction-line filter drier, Liquid-line filter drier
Target: Burnout: suction-line drier + new liquid-line drier, arrows in the direction of flow
Braze the lines in with flowing nitrogen
Flow a trickle of dry nitrogen through the system while brazing the suction and discharge connections so you don't form copper-oxide scale inside the lines (scale plugs metering devices and contaminates the new oil). Keep the regulator low.
Tools: Brazing torch + rod, Nitrogen + regulator
Target: Low flowing-N2 purge during every braze joint
⚠ Never trap nitrogen between two closed points while heating. Fire watch.

Evacuate, charge & verify

Pressure-test, then deep-evacuate to ≤500 microns
Leak-test with nitrogen, then evacuate the system to a deep vacuum with the micron gauge at the system and confirm it holds (decay test) before introducing refrigerant. A wet system kills the new compressor.
Tools: 2-stage vacuum pump, Micron gauge
Target: Evacuate ≤ 500 microns and hold a decay test before charging
Weigh in the nameplate charge
Weigh in the factory charge from the data plate (adjust for line-set length per the charts), then fine-tune by superheat (fixed orifice) or subcooling (TXV).
Tools: Charging scale, Digital manifold + temp probes
Target: Charge to nameplate weight; verify SH/SC after stabilizing
Verify start components, overload & rotation
Confirm the run cap (and start cap/relay/PTC if used), overload, and contactor are correct. On a 3-phase scroll, verify rotation — a backward scroll runs loud, won't pump, and trips on high amps; if so, swap any two line legs. Clamp running amps against RLA.
Tools: Clamp meter
Target: 3-phase scroll must rotate correctly (no loud/howl, builds pressure); running amps ≤ nameplate RLA