Run capacitor
Common no-start and weak-compressor failure point. Match the microfarad and voltage rating.
Carrier WeatherMaker Rooftop Unit Error Codes
Carrier WeatherMaker 48/50 Series RTUs use an LED diagnostic board that flashes fault codes. Count the LED flashes, wait for a 3-second pause, and count again. The total equals the fault code. Some newer units display codes on a 7-segment display.
WeatherMaker Flash Code Table
| Code | Fault Description | Common Cause | Action |
|---|---|---|---|
| 2 | Low-pressure lockout | Low refrigerant, dirty evaporator coil | Check static pressure, inspect filter |
| 3 | High-pressure lockout | Dirty condenser coil, failed condenser fan | Wash coil, check fan rotation |
| 11 | Ignition failure | No gas, weak spark, dirty flame sensor | Check gas pressure (3.5 in. w.c.) |
| 12 | Flame sense fault | Dirty or cracked flame sensor | Clean or replace flame sensor rod |
| 13 | Limit switch open | Restricted airflow, dirty filter | Replace filter, check blower wheel |
| 14 | Ignition lockout | 3 failed ignition attempts | Manual reset required |
| 21 | Gas valve fault | Failed gas valve or wiring issue | Check 24 VAC at gas valve |
| 22 | Low combustion air | Blocked flue, failed inducer | Inspect flue and inducer pressure |
| 23 | Draft safeguard switch | Blocked flue or failed inducer motor | Measure inducer manifold pressure |
| 31 | High-pressure switch open | Refrigerant overcharge, blocked condenser | Check subcooling (10-15 degrees F target) |
| 33 | Limit switch lockout | Persistent overtemperature | Fix airflow restriction before reset |
| 41 | Blower motor fault | Failed blower motor or run capacitor | Check capacitor microF, motor amps |
| 42 | Inducer motor fault | Failed inducer motor or blocked flue | Check inducer amp draw |
| 44 | Control board fault | Internal board failure | Replace IFC board |
| 46 | Power failure | Power interruption detected | Check supply voltage and breakers |
Most Common WeatherMaker Faults
Code 13 - Limit Switch Open
The top commercial RTU call. Work through in order: replace dirty filter, verify all grilles are open, inspect blower wheel for debris, then check limit switch continuity at room temperature.
Code 23 - Draft Safeguard Switch
Measure inducer manifold pressure before condemning the pressure switch. Typical WeatherMaker spec is -0.20 to -0.35 in. w.c. at the pressure switch. A blocked flue screen is a common culprit.
Code 11 - Ignition Failure
Check gas pressure first. Natural gas inlet pressure must be 5-7 in. w.c.; manifold pressure 3.5 in. w.c. Clean the flame sensor rod with steel wool - measure microA (must exceed 1.5 microA).
Code 3 - High Pressure
Verify all condenser fan motors are running and drawing rated amps. Wash the condenser coil. Check refrigerant subcooling with manifold gauges.
Parts Commonly Needed
| Part | Notes |
|---|---|
| Flame sensor rod | Clean first; replace if microA reading is below 1.5 |
| IFC board | Model-specific - cross-reference part number |
| Limit switch | Match temperature rating exactly |
| Run capacitor | Test microF with capacitor tester before condemning motor |
| Inducer motor | Check capacitor before replacing motor |
| Pressure switch | Verify switch spec matches flue pressure measured |
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 WeatherMaker rooftop faults, match parts to the RTU sequence: economizer sensors, gas-heat ignition parts, pressure switches, blower components, fan motors, or control boards by model number.
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 WeatherMaker IFC boards store the last 5 fault codes. Hold the diagnostic button 5 seconds to retrieve fault history before clearing codes.