Carrier Error Code 33: Limit/Rollout Switch Lockout
How to Fix Carrier Code 33
- Step 1: Turn off the furnace at the thermostat.
- Step 2: Check and replace the air filter if it's dirty.
- Step 3: Ensure that all vents (both intake and exhaust) are free from obstructions like snow, ice, or debris.
- Step 4: After waiting a few minutes, turn the furnace back on at the thermostat. If the error reappears, call a qualified HVAC technician immediately.
How to Reset Carrier Code 33
- Turn off the furnace power switch, usually located on or near the unit.
- Turn off the circuit breaker for the furnace. Wait 30 seconds.
- Restore power at the breaker and flip the furnace switch back on.
- Set the thermostat to call for heat. If the error code returns after 2-3 ignition attempts, the fault requires repair.
What does 33 mean?
Error code 33 on your Carrier furnace signifies that the unit's control board has detected an open limit switch or rollout switch for longer than is considered safe. These switches are safety devices designed to shut down the furnace if it overheats or if flames are detected where they shouldn't be (like outside the burner box). The control board locks out after detecting this condition to prevent further operation until the issue is resolved. This lockout requires a manual reset, usually by cycling power to the furnace.
This error is often triggered by a genuine safety concern, such as a blocked vent, a malfunctioning fan, or a cracked heat exchanger. It's crucial to address the underlying cause rather than simply resetting the furnace, as repeated lockouts could indicate a dangerous condition. Ignoring this error can lead to equipment damage, fire, or carbon monoxide poisoning.
Affected Models
- Performance Series Furnace
- Comfort Series Furnace
- Infinity Series Furnace
- Performance Series
- Base Series Furnace
- Performance Boost Furnace
- Performance Boost 95 Furnace
- WeatherMaker 8000
- WeatherMaker 9300
- Infinity 80
- WeatherMaker Furnace
- 24ABC6 Air Conditioner
- 25HBC5 Heat Pump
- Performance Series Heat Pump
- Infinity Series
- Base Series
- Comfort Series
- Infinity Series Heat Pump
- Comfort Series Heat Pump
- Infinity 20 Heat Pump with Greenspeed Intelligence
- Comfort 80 Gas Furnace
Replacement Parts
| Part | OEM Number | Est. Cost |
|---|---|---|
| Limit Switch | KH42WZ008 | — |
| Rollout Switch | LH33WZ557 | — |
| Blower Motor Capacitor | — | — |
Related Codes on Same Models
| Code | Description | Severity |
|---|---|---|
| 11 | No Previous Error | Info |
| 12 | Blower On After Power Up | Warning |
| 13 | Limit/Rollout Fault | Critical |
| 14 | Ignition Lockout | Critical |
| 21 | Gas Heating Lockout | Critical |
| 22 | Abnormal Flame | Critical |
| 23 | Pressure Switch Fault | Warning |
| 24 | Secondary Voltage Fuse | Warning |
| 31 | High Stage Pressure Fault | Warning |
| 32 | Low Flame Sense | Warning |