Carrier Error Code 34: Ignition/Flame Sense Fault
Warning: Your Carrier furnace isn't igniting properly and has locked out. This usually requires professional diagnosis and repair.
LED Blink Pattern
3 short blinks, 4 long blinks.
How to Fix Carrier Code 34
- Step 1: Check your gas supply. Make sure other gas appliances are working.
- Step 2: Check the furnace filter. A dirty filter restricts airflow, which can affect combustion.
- Step 3: Reset the furnace by turning off the breaker for 30 seconds, then turning it back on. If the error returns, call a qualified HVAC technician.
How to Reset Carrier Code 34
- 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.
Resetting clears the code from the display but does not fix the underlying fault. If the code returns after reset, proceed to the diagnostic steps above.
What Does Carrier Error Code 34 Mean?
Error code 34 on a Carrier furnace indicates an ignition or flame sensing issue. The control board isn't detecting a stable flame after the ignition sequence. This can happen for a few reasons, but it usually means the furnace has shut down as a safety precaution. The furnace will likely attempt to restart a few times before locking out completely, displaying the error code.
Common Causes
- Dirty flame sensor
- Weak or intermittent gas supply
- Faulty gas valve
- Blocked or restricted flue
- Ignition control module failure
Diagnostic Steps
| If... | Check | Expected |
|---|---|---|
| Furnace attempts ignition but fails to establish flame | Measure flame sensor microamps (uA) during burner operation. | At least 2 uA DC. Low reading indicates a dirty or faulty sensor. |
| Flame sensor reading is low | Inspect and clean the flame sensor with steel wool or fine emery cloth. | Flame sensor is clean and free of corrosion. |
| Gas pressure suspected | Measure gas pressure at the gas valve with a manometer. | Within the range specified on the furnace rating plate (typically 3.5-4.0 inches water column for natural gas). |
Applicable Carrier Models
- 24ABC6 Air Conditioner(electric)
- 25HBC5 Heat Pump(electric)
- Base Series(gas)
- Base Series Furnace(gas)
- Comfort 80 Gas Furnace(gas)
- Comfort Series(electric)
- Comfort Series Furnace(gas)
- Comfort Series Heat Pump(electric)
- Infinity 20 Heat Pump with Greenspeed Intelligence(electric)
- Infinity 80(gas)
- Infinity Series(electric)
- Infinity Series Furnace(gas)
- Infinity Series Heat Pump(electric)
- Performance Boost 95 Furnace(gas)
- Performance Boost Furnace(gas)
- Performance Series(gas)
- Performance Series Furnace(gas)
- Performance Series Heat Pump(electric)
- WeatherMaker 8000(gas)
- WeatherMaker 9300(gas)
- WeatherMaker Furnace(gas)
Replacement Parts
| Part | OEM Number | Est. Cost | Where to Buy |
|---|---|---|---|
| Flame Sensor | KP29HQ047 | — | Find Part |
| Gas Valve | EF32CW176 | — | Find Part |
| Ignition Control Module | — | — | — |
Related Codes on Same Models
Other codes that affect the same Carrier model families as 34.
| Code | Description | Severity |
|---|---|---|
| 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 |
| 33 | Limit/Rollout Switch Lockout | Critical |