Quick diagnosis
What this code is telling you
Most likely trigger
Gas supply valve shut off or gas line air lock
Recommended replacement
Hot Surface Igniter (HSI)
Diagnostic path
4 ordered checks
Part fit
Exact model number required
Safety first
Before opening the appliance
Unplug the appliance before removing panels or testing internal components. Do not bypass safety switches or live-test high-voltage, gas, refrigerant, or combustion components unless you are qualified to do so.
Read the full safety disclaimerRoot cause
Why the control reported this error
The furnace control locks out or reports this fault when the expected ignition, airflow, pressure, flame, or limit sequence is not proven. Check gas supply valve shut off or gas line air lock first, then verify dirty or defective hot surface igniter and faulty gas valve solenoid coil before replacing hot Surface Igniter (HSI).
Symptoms
What you may notice
- ✓Igniter glows bright orange but gas fails to catch light
- ✓Furnace retries 3 times then enters 1-hour soft lockout
- ✓Display shows code 11
Possible causes
Check the most likely causes first
- 1
Gas supply valve shut off or gas line air lock
Start here when it matches your symptoms.
- 2
Dirty or defective hot surface igniter
- 3
Faulty gas valve solenoid coil
- 4
Sooted flame sensor
Diagnostic sequence
Work through these checks in order
Stop when you find the fault. Do not perform a step that requires skills or live testing you are not qualified to do.
- 1
Check 1
Disconnect electrical power before opening panels. Confirm shutoff gas valve handle is parallel to pipe line.
- 2
Check 2
Disconnect electrical power before opening panels. Check igniter for white hot spots or cracks; test resistance (typical 40-90 ohms).
- 3
Check 3
Clean flame sensor probe with steel wool.
- 4
Check 4
Replace hot surface igniter.
Replacement part reference
Hot Surface Igniter (HSI)
Exact OEM part number
Model number required
Fitment note
The exact OEM part number varies by model and production revision. Verify the complete model number before ordering.
Verify the appliance model before ordering.
Manufacturers can use different parts under the same error code across model families and production revisions.
Where do I find my model number? →FixCodeDB may earn a commission from qualifying purchases made through affiliate links.
Common questions
Quick answers for this fault
What should I check first for 11?
Start with gas supply valve shut off or gas line air lock. If that checks out, continue through the diagnostic sequence above rather than replacing a part based on the code alone.
Does 11 always mean Hot Surface Igniter (HSI) is bad?
No. An error code identifies the condition the control detected, not a guaranteed failed part. Confirm the likely causes and wiring first. The exact OEM part number varies by model and production revision. Verify the complete model number before ordering.
When should I stop troubleshooting 11 myself?
Stop if the next step requires live electrical testing, sealed-system work, gas or combustion service, or any procedure outside your training. Unplug the appliance before removing panels or testing internal components. Do not bypass safety switches or live-test high-voltage, gas, refrigerant, or combustion components unless you are qualified to do so.
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