Carrier 24ACC636A003 Comfort Series AC MECH-TXV Error Fix: Thermostatic Expansion Valve (TXV) Failure — Poor Cooling or Freezing

Error code MECH-TXV on the Carrier 24ACC636A003 Comfort Series AC means: Thermostatic Expansion Valve (TXV) Failure — Poor Cooling or Freezing. The thermostatic expansion valve regulates refrigerant flow into the evaporator coil. When it fails, it causes either too much or too little refrigerant flow. TXV stuck closed: very low refrigerant flow → high superheat at the compressor → compressor overheating → poor cooling → potential compressor damage. Symptoms: warm air from vents, frost on the liquid line at the outdoor unit, compressor running hot. TXV stuck open: excessive refrigerant flow → liquid refrigerant floods back to the compressor → low superheat → compressor slugging and potential liquid damage. Symptoms: iced-over evaporator coil, gurgling or hissing sounds from the indoor coil, and potentially liquid refrigerant making it back to the compressor. Diagnosis requires measuring superheat and subcooling with refrigerant gauges and temperature clamps. TXV replacement costs $300-$800 installed. Some Carrier models use a piston/orifice instead of a TXV — these are simpler and cheaper to replace.

The most successful fix is "Test and Replace the Thermostatic Expansion Valve (TXV)" (hard difficulty, ~90 minutes). Estimated DIY cost: $0-$20. HomeMD has 2 community-ranked fixes for this error.

This error is rated medium severity. It should be addressed soon, but your appliance may still function in a limited capacity.

Yes — the top-ranked community fix ("Test and Replace the Thermostatic Expansion Valve (TXV)") is rated hard difficulty and takes about 90 minutes. Tools needed: Refrigerant manifold gauge set, Temperature clamp thermometer, Vacuum pump, Teflon wrench, Adjustable wrench, Refrigerant recovery machine.

DIY cost: $0-$20. Professional repair typically costs $400-$800. Many homeowners save money by trying the top-ranked community fix first.

The Carrier 24ACC636A003 Comfort Series AC has 8 other known error codes, including: MECH-CAPACITOR (Run Capacitor Failure — AC Hums But Won't Start, or Shuts Off), MECH-COMPRESSOR (Compressor Failure — No Cooling, Loud Noises, or Tripping Breaker), MECH-CONDENSER-COIL (Condenser Coil Fouling — Reduced Cooling and High Pressure), MECH-CONTACTOR (Contactor Failure — AC Won't Turn On or Won't Turn Off), MECH-FAN-BLADE (Condenser Fan Blade Issues — Vibration and Noise), and 3 more.

Error code MECH-TXV also appears on 2 other Carrier models: 24ACB748A003 3 Ton 14 SEER Central Air Conditioner Condenser, Carrier 26SCA5 Comfort 16 Single-Stage Air Conditioner (Up to 16 SEER2). The fix may vary by model, so check each model's specific page for tailored repair steps.