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°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 ┬╡F, 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 ┬╡A (must exceed 1.5 ┬╡A).
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 | Amazon | Clean first; replace if ┬╡A reading is below 1.5 |
| IFC board | Amazon | Model-specific — cross-reference part number |
| Limit switch | Amazon | Match temperature rating exactly |
| Run capacitor | Amazon | Test ┬╡F with capacitor tester before condemning motor |
| Inducer motor | Amazon | Check capacitor before replacing motor |
| Pressure switch | Amazon | Verify switch spec matches flue pressure measured |
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.