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Rinnai Code 12 — Flame Failure
Your Rinnai lit, then lost the flame while running. That points to gas pressure dropping under demand, a dirty flame rod, or a combustion-air problem.
What Code 12 Means
Code 12 means the burner ignited but then lost its flame during operation. The unit senses the flame is gone and shuts down. Unlike Code 11 (never lit), Code 12 is about the flame not staying lit — which usually means the gas or combustion conditions can't sustain it.
The usual causes are gas pressure sagging when the unit ramps up or another appliance kicks on, a flame rod that's dirty or failing so it can't confirm the flame, or a venting/combustion-air problem. We verify gas pressure under load and inspect the flame rod.
Common Causes of Code 12
1. Gas pressure under load
If pressure drops when the unit ramps up or another gas appliance runs, the flame starves and drops out. A common cause on undersized gas lines.
2. Dirty or failing flame rod
The flame rod confirms the flame is present. When it is dirty or degraded, the unit can't verify the flame and shuts down even though it lit.
3. Venting or combustion air
A partial venting restriction or poor combustion air can destabilize the flame. We check the vent and intake.
4. Gas valve issue
A gas valve not modulating correctly can let the flame drop under certain conditions. Tested after supply and flame rod.
Rinnai Code 12 FAQs
Why South Shore homeowners choose Johnson Bros.
Rinnai showing Code 12? Tell us the model and we'll triage.
Every Rinnai model reads codes a little differently. Have your model number handy and we'll tell you whether it's a quick fix or a service visit.
Need help fast? Call for urgent plumbing issues. Booking online is best when you want the next open appointment without waiting on the phone.
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Rinnai showing Code 12? Tell us the model and we'll triage.
Every Rinnai model reads codes a little differently. Have your model number handy and we'll tell you whether it's a quick fix or a service visit.
Call for urgent help now. Book online when you want the next available fit for your schedule.