Rheem Furnace Code 13 – Fixed

Rheem furnaces are known for their fast heating times and energy efficiency. They are also designed with safety sensors that automatically turn the furnace off if it overheats or is damaged, which may result in an error code. 

Rheem Furnace Code 13 indicates a flame rod problem, which can cause the furnace to overheat. This error code will cause your Rheem furnace to shut down for 6 hours. Easy fixes include cleaning or replacing the flame rod and checking for airflow blockages. 

In this article, I’ll discuss the reasons for an error code 13 on a Rheem furnace. I’ll also take you through easy fixes that you can try before calling a repair professional. 

1. There Is Residue on the Flame Rod 

A buildup of rust or dirt on a Rheem furnace’s flame rod is the main cause of error code 13. This will affect the flame length and may result in overheating, causing the furnace to shut off. 

The sensors on the flame rod can also detect excess rust or dirt, and this may cause multiple errors. So, even if the furnace doesn’t heat up, but there’s a dirt buildup on the flame rod, you’ll see an error 13. 

a home high efficiency furnace with a residential gas water heater & humidifier

How To Fix 

Before removing whatever is interfering with the flame rod’s sensors, you should open the furnace to examine the rods. To avoid the risk of electrocution, always switch off the power source before attempting a repair or when you see an error code. 

Consult your furnace’s manual to locate the flame rod and examine it from a distance. If you notice rust or dirt around it, gently remove it with a soft cloth. For stubborn rust deposits, use a small piece of steel wool and gently rub it off. 

Place the flame rod back into the furnace and restart it. 

If deposits on the flame rod were the issue, you shouldn’t receive another code 13 error. If you still see the error, consider the fixes below. 

2. The Flame Rod Is Damaged 

If dirt or rust isn’t damaging the flame rod, the code 13 error may be due to a damaged flame rod. The flame rod may be cracked or broken, disrupting the furnace’s flame control. This may cause the furnace to overheat, and the error code will appear after the furnace shuts down. 

Before checking the flame rod, wait a few hours for the furnace to restart. If the furnace restarts successfully and you don’t get another code 13 error, there’s no need to worry. If you see the error code after troubleshooting your Rheem furnace, you should check the flame rod.

How To Fix 

Disconnect the furnace’s power source and follow the manual’s instructions to locate the flame rod. Examine the flame rod for cracks and check the rod’s tip very carefully. If you notice any distortions or the flame rod is bent, the only solution is to replace it. 

Always contact a Rheem furnace technician if you suspect that your furnace has a damaged flame rod. If you have a relatively new furnace, you may still have time left on the warranty, and you’ll get a free replacement. 

If your warranty is over, you will need to pay for the replacement part yourself. 

3. The Air Filter Is Dirty 

A dirty air filter may affect the air circulation inside the Rheem furnace, causing it to overheat. This is a very common problem, especially for people who live in the inner city or a dusty area. 

air filter

If you know your way around your Rheem furnace, you’ll know where the air filter is located. If not, check how to remove the filter from the manual and examine it. 

How To Fix 

If the air filter is dirty, you should clean it. Depending on your furnace type, you can clean the air filter with warm soapy water and a soft brush. Do not damage the filter fabric, as this could affect the furnace’s air circulation. 

Here is a video guide on how to clean a furnace’s air filter: 

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4. The Exhaust Vents Are Blocked 

Like the air filter, the exhaust vents play an important role in regulating the furnace’s temperature. The exhaust vents may be blocked if you haven’t serviced the furnace in a while. Sometimes, pests may also somehow make their way into these vents and block them. 

How To Fix 

If there’s an obstruction in your furnace’s exhaust vents, remove it if it’s safe to do so. If the vents are very dirty or you don’t feel comfortable cleaning them, have a professional HVAC service do the job for you. Ideally, you should service the furnace twice a year and clean the vents annually to prevent blockages. 


If you see error code 13 on your Rheem furnace, it’s usually because of a damaged or dirty flame rod. You’ll need to clean or replace the flame rod in such cases. 

The other causes of a code 13 error are blocked air vents or a dirty air filter. However, you shouldn’t have these issues if you service your furnace regularly.