Run capacitor
Common no-start and weak-compressor failure point. Match the microfarad and voltage rating.
Carrier Infinity 24ACC6 Error Codes — What They Mean
The Carrier Infinity 24ACC6 is a high-efficiency single-stage central air conditioner designed to operate within Carrier’s Infinity communicating system. It uses a two-speed or variable-speed blower paired with an Infinity touch thermostat and communicates faults through both the thermostat display and a diagnostic LED on the outdoor control board. Flash codes appear when the unit is in standalone (non-communicating) mode; alphanumeric codes appear on the Infinity thermostat in full communicating mode.
Carrier 24ACC6 Error Code Reference
| Code / Flash | Meaning |
|---|---|
| 2 flashes | High-pressure switch open |
| 3 flashes | Low-pressure switch open |
| 4 flashes | Compressor protection active |
| 5 flashes | Outdoor control board fault |
| 6 flashes | Outdoor ambient temperature sensor fault |
| 7 flashes | Discharge line temperature sensor fault |
| 8 flashes | Communication bus fault (Infinity link) |
| 11 flashes | Thermistor fault — outdoor coil sensor |
| Thermostat: 174 | High-pressure trip |
| Thermostat: 175 | Low-pressure trip |
| Thermostat: 178 | Compressor communication fault |
| Thermostat: 179 | Outdoor fan fault |
Common Causes by Code
- Code 2 / Error 174 — High pressure — Dirty condenser coil, failed outdoor fan motor, or refrigerant overcharge. The 24ACC6 uses R-410A and is factory-charged; overcharge usually follows an improper service event.
- Code 3 / Error 175 — Low pressure — Refrigerant leak, failed low-pressure switch, or ambient temperature below 40°F without the low-ambient kit installed. Inspect Schrader valves and service port caps — they are common leak points on older units.
- Code 4 — Compressor protection — Compressor internal overload or low line voltage. The 24ACC6 compressor overload resets automatically after 20–30 minutes. Check capacitor before suspecting a failed compressor.
- Code 8 / Error 178 — Communication fault — Broken Infinity control wire between thermostat, air handler, and outdoor unit. Also triggered by a failed Infinity board or thermostat.
- Code 11 — Coil thermistor — The outdoor coil temperature sensor is mounted on the liquid line. Corrosion or a loose connector is the typical cause. Resistance should follow the NTC thermistor curve in the service manual.
Step-by-Step Fix
- Check the thermostat display first — In communicating mode, the Infinity touch thermostat shows alphanumeric fault codes directly. Navigate to System > Diagnostics to view all active and historical alerts.
- For Code 2 / high pressure — Turn the unit off at the thermostat. Inspect the condenser coil for fouling — cottonwood, grass clippings, and pet hair accumulate along the coil base. Flush from inside-out with a garden hose. Confirm the condenser fan is drawing air upward.
- For Code 3 / low pressure — Connect manifold gauges (R-410A). Suction pressure should be 100–115 PSI at 70°F ambient. Low charge requires finding the leak before adding refrigerant. Use an electronic leak detector at service ports, coil connections, and line set fittings.
- For Code 8 / communication — Check the control wire for damage (staples through the wire are a common installation defect). Verify the wire is connected to the correct terminals on all three components. Test voltage at the board.
- Clear faults — Power cycle the outdoor disconnect, wait 30 seconds, and restore power. Monitor for fault recurrence within the first cooling cycle.
Parts Often Needed
| Part | Notes |
|---|---|
| Run capacitor | Dual run capacitor for compressor and fan motor |
| Contactor | Check for pitted or welded contacts |
| Low-pressure switch | Replace if Code 3 persists with correct charge |
| Outdoor coil thermistor | For Code 11; inexpensive OEM part |
| Infinity control board | For persistent Code 5 or communication faults |
| Condenser fan motor | Confirm correct rotation before condemning |
Technician Tips
Carrier uses different diagnostic systems across furnaces, heat pumps, chillers, mini-splits, VRF equipment, rooftop units, and communicating controls. Confirm the full model number and whether the fault came from the indoor board, outdoor board, thermostat, or equipment controller before matching it to a repair path.
Start with power, wiring, airflow or water-flow, sensor, condensate, and safety-circuit checks before ordering control boards. If the same code returns after one reset and the basic cause is not obvious, test the named circuit instead of repeatedly cycling the equipment.
Parts note: For Infinity 24ACC6 faults, match parts to the outdoor unit and Infinity communication path: sensors, pressure switches, control boards, communication wire, and fan components.
Need Replacement Parts?
Before ordering, match the HVAC part to the model number, electrical rating, and failure symptom. Check current prices on Amazon - prices and availability change frequently.
When to Call a Pro
Refrigerant work requires EPA 608 certification. Infinity system communication faults can require Carrier Service Advisor software (ICP/SA) to perform advanced diagnostics — this is a dealer-level tool not available to the general public. If the Infinity thermostat is showing fault codes not covered in the standard code list, contact a Carrier factory-authorized dealer.