Temperature sensor
Common error-code part. Confirm resistance and connector style.
Carrier Greenspeed Heat Pump Error Codes
Carrier Greenspeed heat pumps (25VNA series) use the Infinity communicating system. All fault codes display on the Infinity thermostat (SYSTXCCITC01-B or similar). These units use a variable-speed inverter compressor - fault codes include inverter-specific issues.
Greenspeed Fault Code Table
| Code | Fault Description | Common Cause | Action |
|---|---|---|---|
| 11 | Ignition failure (gas) | N/A for heat pump | Check system configuration |
| 24 | Low-voltage fuse blown | Short in low-voltage wiring | Check all 24 VAC wiring |
| 25 | Reversing valve fault | RV stuck or solenoid issue | Check solenoid, measure RV temps |
| 31 | High-pressure switch | Dirty coil, overcharge | Wash coil, check charge |
| 32 | Low-pressure switch | Low charge or low ambient | Check refrigerant charge |
| 33 | Limit switch lockout | Air handler fault | Check AHU filter and motor |
| 41 | Inverter drive fault | Inverter board, DC bus | Check inverter LED, DC bus voltage |
| 42 | Low DC bus voltage | Input voltage problem | Check supply voltage |
| 43 | High DC bus voltage | Input voltage spike | Check voltage and surge protection |
| 44 | Inverter over-temperature | Inverter heatsink hot | Check inverter fan, clearances |
| 45 | Compressor fault | Compressor protection tripped | Check amps, check for locked rotor |
| 51 | Outdoor coil sensor fault | Failed sensor | Check resistance at sensor |
| 52 | Outdoor ambient sensor | Failed OAT sensor | Replace sensor |
| 61 | Indoor coil sensor fault | Failed sensor at AHU | Check sensor at indoor unit |
| 65 | Communication fault | Infinity bus wiring | Check Infinity network wiring |
Most Common Greenspeed Faults
Code 41 - Inverter Drive Fault
The most complex fault on Greenspeed units. Check inverter board LEDs first - they display a secondary fault code. Measure DC bus voltage at inverter board terminals (target 300-350 VDC on 240 VAC input). A weak capacitor or failed transistor are common causes.
Code 31 - High-Pressure Switch
Greenspeed units use R-410A with a high-side limit of 590 psi. Dirty condenser coils or insufficient outdoor airflow are the most common causes. Check condenser fan motor operation - Greenspeed uses variable-speed condenser fans.
Code 65 - Communication Fault
The Infinity bus uses a shielded 2-wire system. Any loose connection or short causes erratic communication faults. Check all Infinity wire connections at the outdoor unit, thermostat, and indoor unit.
Parts Commonly Needed
| Part | Notes |
|---|---|
| Inverter board | Carrier part number critical - match model |
| Infinity thermostat | Required for code display and diagnostics |
| Defrost sensor | 10kohm thermistor type |
| High-pressure switch | Match R-410A setpoint |
| Outdoor fan motor | Variable speed - match HP and RPM |
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 Greenspeed heat-pump faults, use the exact outdoor-unit model to source sensors, pressure switches, inverter boards, fan motors, reversing-valve coils, and communication parts.
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.
Pro tip: Carrier Infinity systems retain up to 12 fault codes with timestamps. Access via thermostat -> Menu -> Diagnostics -> Fault History. Review history before clearing to identify recurring issues.