MEDIUM URGENCY

Rheem Code 13 - Flame Lost

Code 13

Flame established but lost mid-cycle.

Brand: Rheem (Also covers Ruud) | Equipment: Gas Furnace

What This Code Means

Code 13 means the Rheem (Ruud) furnace lit the burners but flame was lost before the heating cycle completed. Often due to flame sensor degradation or unstable gas pressure.

Likely Causes (Ranked)

Most common

Dirty flame sensor

What: Sensor loses signal mid-cycle due to coating.

How to check: Pull and inspect.

Fix: Clean with emery cloth.

Shop parts

Common

Unstable gas pressure

What: Pressure drops during heating cycle, flame goes out.

How to check: Tech measures gas pressure under load.

Fix: Adjust regulator or call gas utility.

Less common

Cracked burner or misalignment

What: Burner damage disrupts flame stability.

How to check: Tech visual inspection.

Fix: Replace burner assembly.

Diagnostic Steps

Clean flame sensor
Watch a complete heat cycle
Check burner flame appearance
Call tech for gas pressure issues

Frequently Asked Questions

What does Rheem code 13 mean?

Flame lost during operation - the furnace lit but flame went out mid-cycle. Usually a dirty flame sensor.

How urgent?

Same-day attention recommended. Recurring code 13 progresses to lockout.

Same on Ruud?

Yes.

Related Rheem Codes

Related Symptoms

Need More Help?

Try our interactive symptom diagnostic tool or browse Rheem parts.

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