MEDIUM URGENCY

Rheem Code 10 - One-Hour Lockout

Code 10

One-hour soft lockout after repeated ignition failures.

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

What This Code Means

Code 10 on a Rheem furnace (also Ruud) means the control entered a 1-hour soft lockout after multiple failed ignition attempts. The furnace will retry automatically after 60 minutes, but the underlying issue must be fixed or it will lock out again.

Likely Causes (Ranked)

Most common

Dirty flame sensor

What: Coated sensor can't detect flame; control thinks ignition failed.

How to check: Pull and inspect for soot.

Fix: Clean with fine emery cloth.

Shop parts

Common

Failed igniter

What: Igniter not reaching ignition temperature.

How to check: Watch for orange glow.

Fix: Replace igniter.

Shop parts

Common

Gas supply issue

What: Closed valve or low pressure.

How to check: Verify gas valve open; test other appliances.

Fix: Open valve or call gas utility.

Diagnostic Steps

Cut power 60s to force-clear lockout
Watch heat cycle
Clean flame sensor
Replace igniter if no glow
Call HVAC tech if persistent

Frequently Asked Questions

How to reset Rheem code 10?

Cut power 60s. Or wait 1 hour for auto-retry. But the underlying problem must be fixed or it'll return.

Same code on Ruud?

Yes - Rheem and Ruud are sister brands using identical control boards and codes.

Why does code 10 repeat?

Repeated ignition failure means persistent issue. Start with flame sensor cleaning.

Related Rheem Codes

Related Symptoms

Need More Help?

Try our interactive symptom diagnostic tool or browse Rheem parts.

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