Rheem Furnace Error Codes List

Summary

A blinking LED on a Rheem furnace indicates a diagnostic code that helps identify specific issues.
Common error codes include ignition failure, flame detection issues, and high limit switch problems, each with specific troubleshooting steps.
For serious issues like a triggered rollout switch, immediate shutdown and professional assistance are necessary.
DIY fixes can include changing air filters and cleaning flame sensors, while persistent errors or gas smells require a technician.
Properly resetting the furnace after addressing issues is crucial to ensure the problem is resolved and the furnace operates safely.

Your Furnace Is Trying to Tell You Something

The house is cold, your furnace is silent, and there it is—a blinking LED on the control board. What now?

If you own a Rheem furnace, that little light isn’t random. It’s a diagnostic code, and it’s doing you a favor. Instead of leaving you guessing (or shelling out hundreds for a quick fix), your furnace is speaking in blinks—coded messages that pinpoint exactly what’s going wrong.

And once you learn to speak its language? You’ve got power. You’ve got options. And you might just save yourself from a freezing night and a hefty repair bill.

How to Read the Blinking LED Codes

First, locate the control board panel—typically behind the main furnace door. There, you’ll find a blinking light. The pattern isn’t just for show—it’s the code.

Single LED models: One light blinking in short or long bursts = the code.
Dual LED models: One LED gives the first digit, the second gives the second.
(Example: 1 blink, then 2 blinks = code 12)

Let the pattern run twice to confirm. It resets every few seconds, so don’t rush.

The Ultimate Rheem Error Code Decoder

Here’s a breakdown of the most common Rheem furnace error codes and what they actually mean—no tech manual required:

Code	What It Means	What You Can Do
1	Ignition failure	Check ignitor, flame sensor, gas line
2	Flame not detected	Clean flame sensor—gently, no chemicals
3	Pressure switch stuck open	Inspect venting, drain lines, or inducer fan
4	High limit switch open (overheat)	Replace air filter, open closed vents
5	Flame sensed when off	May be a faulty board or stuck gas valve
6	Pressure switch stuck closed	Check for blockages in exhaust piping
7	Rollout switch triggered (flame outside burner)	Dangerous. Turn off furnace. Call a pro.
8	Blower motor fault	Could be capacitor, relay, or motor failure
9	Control board issue	Check for burnt spots or replace board
10	Weak flame signal	Clean sensor or verify burner performance
12	Lockout due to repeated failures	Reset furnace after correcting problem
13	Limit switch locked out	Happens after repeated overheating
14	Incorrect line voltage	Check electrical connections, grounding

Most Common Codes (and What to Do)

Code 2 – Flame Not Detected
This one shows up a lot. Your furnace starts up, ignites, then shuts down—fast.
Fix: Turn off power. Remove and gently clean the flame sensor. Reinstall firmly.

Code 4 – High Limit Switch Open
Translation: the furnace is running too hot.
Fix: Start with your air filter. If it’s clogged, replace it. Also, check that vents aren’t blocked.

Code 7 – Rollout Switch Triggered
This is a serious one. It means flames went where they shouldn’t.
Fix: Shut down immediately. Do not reset. This is a fire risk—call a pro.

Code 12 – Repeated Failures Lockout
The furnace tried to start too many times and gave up.
Fix: Reset the unit after fixing the root issue (sensor, ignitor, airflow, etc.).

How to Reset a Rheem Furnace After Fixing an Error

Once you’ve addressed the issue:

Turn off power at the wall switch or breaker.
Wait 60 seconds.
Flip power back on.
Watch the LED panel—if it flashes slowly or stays solid, you’re in the clear.

If the same code returns, the issue may still be unresolved—or you’ve got a deeper problem on your hands.

When to DIY vs When to Call a Technician

✅ You Can Handle:

Replacing air filters
Cleaning the flame sensor
Checking vent blockages
Basic resets

🚫 Call a Pro If:

Error codes repeat after resets
You see code 7 or smell gas
The control board blinks erratically
You’re uncomfortable handling electrical components

Remember: decoding the code is step one. Fixing it right—and safely—is what gets the heat flowing again.

Products / Tools / Resources

Flame Sensor Cleaning Tools: Fine steel wool or emery cloth
Smart Thermostats Compatible with Rheem: EcoNet, Nest, ecobee
Error Code PDFs by Model: rheem.com
Furnace Pro Locator: rheem.com/find-a-pro

Rheem Furnace Error Codes List: What Every Blinking Light Really Means

Summary

Your Furnace Is Trying to Tell You Something

How to Read the Blinking LED Codes

The Ultimate Rheem Error Code Decoder

Most Common Codes (and What to Do)

How to Reset a Rheem Furnace After Fixing an Error

When to DIY vs When to Call a Technician

Products / Tools / Resources