Rheem Criterion Ii Gas Furnace Troubleshooting

If your Rheem Criterion II gas furnace troubleshooting session has turned into a cold house and a blinking LED, you're not alone. This model, built mostly between the mid‑1990s and early 2000s, uses a single‑stage gas valve, hot surface ignition, and an Integrated Furnace Control (IFC) board that communicates errors through a small LED light.

That LED is your best tool. In our research, nearly every common Criterion II failure can be traced back to one of about a dozen error codes. Once you learn to read it and follow the right branch, you can save yourself a service call.

Let's walk through the diagnosis step by step.

Quick Answer

Start by reading the LED blink code on the IFC board. That code tells you which component is failing. Common issues include a dirty flame sensor, a bad igniter, a tripped pressure switch, or a stuck limit switch.

Reset the furnace by turning off the breaker for five minutes. If the error returns, follow the decision tree below for your specific blink code.

First Things First: Is Your Criterion II in Lockout?

Before opening any panels, check whether the furnace has gone into safety lockout. The IFC board stops trying after three failed ignition attempts. The symptom is simple: no heat, the blower runs for a few seconds then stops, and the LED shows a steady error code.

To reset it, turn off the dedicated circuit breaker for the furnace. Wait at least five minutes. This gives the board time to power down and clear stored faults.

Flip the breaker back on. If the furnace fires up within 30 seconds and runs for more than five minutes, you're done. If it locks out again, you have a real problem.

Do not keep resetting repeatedly. Each reset is a band‑aid. The lockout means the furnace detected a failure.

You need to read the error code before proceeding.

Read the Blink Code: What That Little LED Is Telling You

Open the upper access panel. On the left side of the blower compartment, you'll see the IFC board. Near the center is a tiny LED.

Count the number of times it blinks, then the pause, then count again.

Here are the most common codes for the Criterion II:

Write the code down. That number tells you exactly which branch to follow. Code 2 means jump to the igniter and flame sensor checks.

Code 3 or 7 points to the pressure switch and venting.

Branch 1: No Heat But the Blower Runs

If the blower comes on but the furnace never ignites, the issue is likely in the thermostat circuit, the limit switches, or the control board.

First, isolate the thermostat. Remove the thermostat cover. Touch the R terminal to the W terminal with a short piece of wire.

This bypasses the thermostat. If the furnace fires up, the thermostat is bad or its wiring is faulty.

If that does nothing, check the rollout limit switch on the burner box. It has a small red reset button in the center. Gently press it until it clicks.

If the furnace starts, you had a nuisance trip. But you must clean the burners and check the vent for blockages, or it will trip again.

If the blower still runs but burners never light, you probably have a failing IFC board. On Criterion II models, the board is often the culprit on units older than 15 years. Replacements run about $120 to $180 from Rheem distributors.

Always match the part number from your model's spec sheet.

Branch 2: Igniter Glows But No Flame

This is the most common call on this furnace. You hear the inducer motor spin up. You see the hot surface igniter glow orange.

Then no flame appears.

Start with the obvious. Is the gas turned on? Check the valve on the gas line.

It should be parallel to the pipe. If it is perpendicular, open it and wait a few minutes for air to purge.

If gas is on, test the igniter. Unplug the two‑pin connector. Use a multimeter set to ohms.

Measure across the igniter pins. A cold igniter should read between 10 and 50 ohms. If it reads open (infinite), it is dead.

Replace it. If it reads shorted (under 5 ohms), it may still glow but will not reach the right temperature. Replace it too.

Next, check the gas valve. With the igniter glowing and the call for heat active, measure the voltage across the two wires coming into the gas valve. You should see 24 VAC.

If you see voltage and the valve does not open, the valve coil is likely burned out. Replace the gas valve. If you see no voltage, the IFC board is not sending power.

Do not forget the flame sensor. A dirty flame sensor causes the burner to light but shut down after five to ten seconds. Remove the sensor.

Clean it gently with steel wool or a Scotch‑Brite pad. Reinstall it. Per Rheem service bulletins, a flame sensor reading below 1.5 microamps DC will make the board shut down.

Branch 3: Furnace Short Cycles or Trips Limits

If your Criterion II runs for two to five minutes then shuts down, you are dealing with a limit switch issue. The high‑limit switch stops the burner if the heat exchanger gets too hot. That is almost always an airflow problem.

First, check the air filter. A dirty filter is the number one cause of short cycling on this model. Pull it out.

Hold it up to light. If you cannot see through it, replace it. Use a one‑inch thick pleated filter.

Do not upgrade to a heavy MERV 13 filter. It restricts airflow too much for an 80% furnace like the Criterion II.

Next, inspect the blower motor capacitor. A failing capacitor makes the blower turn slower than intended. It is located on the side of the blower housing.

Check for bulging or leaking. Use a multimeter with capacitance function to test. The measured value should be within 10% of the rating stamped on the side.

Replace it if out of spec.

Do not ignore the pressure switch. If the draft inducer motor is not pulling enough vacuum, the pressure switch never closes. You will get blinks 3 or 7.

Check the hose from the inducer to the switch. It can become clogged with spider webs or debris. Also check the vent termination outside for bird nests or snow blockage.

Branch 4: Blower Won't Stop, Won't Start, or Hums

A blower that runs constantly after the call for heat ends usually points to the fan limit switch. This switch tells the blower when to turn on and when to shut off. If it sticks closed, the blower keeps running.

Test it with a multimeter set to continuity. With the furnace off and the switch at room temperature, the terminals should show an open circuit. If they show continuity, replace the fan limit switch.

It costs around $25 from a Rheum distributor.

A blower that will not start at all or just hums is often a dead run capacitor. A bulging top or visible leaking means it is bad. Test it with a capacitance meter.

If the reading is more than 10% off the stamped value, replace it.

Before you dig deeper, check the door interlock switch. This is the spring‑loaded button that the upper access panel presses against. If the panel is not fully seated, the switch stays open and the blower will not run.

Push the button manually with the panel off. If the blower starts, you found the issue.

A broken thermostat wire is the last easy check. Use a multimeter to check continuity on each wire. Replace any damaged wiring.

Common Mistakes DIYers Make on the Criterion II

The most dangerous mistake is bypassing the pressure switch. Jumping the switch with a paperclip forces the furnace to run even when the vent is blocked. That sends carbon monoxide into your home.

Never do it.

Another common error is resetting the rollout switch without checking for a flame rollout first. A tripped rollout switch means the burner flames are rolling out of the burner box. That can happen from a blocked heat exchanger or dirty burners.

If you reset it without cleaning the burners and checking the vent, the fire risk remains.

Skipping the door interlock check is also a frequent miss. People assume the blower is dead when the real problem is just an unseated panel. It takes two seconds to test.

Using the wrong replacement parts is another headache. The Criterion II uses specific igniters and gas valves. A universal aftermarket igniter might fit but draw the wrong current.

That can damage the IFC board. Always match the part number from your model's spec sheet.

Finally, do not ignore the flame sensor. It is a cheap fix. A dirty sensor causes the burner to light and then shut down after ten seconds.

Cleaning it with steel wool takes one minute and saves a service call.

Rheem Criterion II Troubleshooting FAQ

Where is the model number on my Rheem Criterion II furnace?

Look inside the upper access panel on the left side of the blower housing. It is printed on a white sticker. The format is usually RGED-07EAMER or similar.

How do I reset my Rheem Criterion II furnace?

Turn off the dedicated circuit breaker for the furnace. Wait five minutes. Turn it back on.

This clears the IFC board memory and resets the lockout.

Why does my furnace light but then go out after a few seconds?

A dirty flame sensor is the most likely cause. Remove the sensor. Clean it gently with steel wool or a Scotch‑Brite pad.

Reinstall it. If that does not fix it, test the gas valve voltage.

Can I convert my Criterion II to propane?

Yes, but only with the correct LP conversion kit. The kit includes a different gas valve orifice and a spring change. Running natural gas through an LP valve is dangerous.

When should I call an HVAC professional?

Call a pro if you smell gas, if the rollout switch keeps tripping after cleaning the burners, or if you test the ignition components and still cannot find the problem. Some repairs, like gas valve replacement, require a licensed technician.

How long does a Rheem Criterion II furnace last?

With regular maintenance, these furnaces typically last 18 to 22 years. Parts availability is still good as of 2026. Replacement may be more cost-effective if the heat exchanger fails.