Rheem Criterion II furnace issues often stem from ignition, airflow, or control board faults.
I’ve worked on gas furnaces for years and have hands-on experience with Rheem units, including the Criterion II series. This guide on Rheem Criterion Ii Gas Furnace Troubleshooting walks you through safe diagnostics, common faults, step-by-step fixes, and maintenance tips. Read on to learn practical steps you can do yourself, when to call a pro, and how to prevent recurring problems.
Common symptoms and what they mean
Understanding symptoms helps you target Rheem Criterion Ii Gas Furnace Troubleshooting quickly. Below are frequent signs and their likely causes.
- Furnace won’t start
Usually a power, thermostat, or ignition problem. Check breakers, switches, and thermostat settings first. - Furnace cycles on and off quickly (short cycling)
Could be overheating from blocked airflow or a failed limit switch. - No heat but blower runs
Often an ignition failure or gas valve issue. - Blower runs constantly
Could be a fan limit control, thermostat fan setting, or control board fault. - Strange noises or rattles
Loose panels, failing bearings, or flame rolling out can cause sounds. - Flame problems: yellow flame, high heat, or noisy burner
Combustion issues, dirty burners, or pressure problems are common.
These quick matches make Rheem Criterion Ii Gas Furnace Troubleshooting faster and more accurate.
Safety first: before you start troubleshooting
Safety is essential in any Rheem Criterion Ii Gas Furnace Troubleshooting. Take precautions every time.
- Turn off power at the furnace switch and breaker before opening panels. Electricity can be fatal.
- Shut off gas at the gas valve if you smell gas or are working near gas components.
- Use a multimeter to check voltages only if you know how. Otherwise, call a technician.
- Work in a well-ventilated area and keep flames or sparks away. Gas leaks are dangerous.
- Wear gloves and eye protection. Furnace parts can be sharp and hot.
If you smell gas strongly, leave immediately and call your gas company or emergency services. Don’t attempt repairs until a technician confirms safety.
Step-by-step Rheem Criterion Ii Gas Furnace Troubleshooting guide
Follow these steps in order. They are practical and safe for a homeowner with basic tools.
- Check basics first
- Confirm thermostat is set to heat and the temperature setpoint is above room temp.
- Check the furnace switch and main breaker. Reset if tripped.
- Replace thermostat batteries and confirm wiring is secure.
- Inspect air filter and airflow
- A clogged filter causes many faults and short cycling. Replace or clean the filter.
- Ensure vents and returns are open and unobstructed.
- Observe the furnace start sequence
- Turn the thermostat up and watch the furnace. Note any delays or error LED patterns.
- If you hear the inducer motor, ignition sequence may follow. No sound suggests a control, transformer, or safety lockout.
- Check the pilot or ignition system
- Older Criterion II may use standing pilot or intermittent pilot. Confirm pilot flame is steady and blue.
- For electronic ignition, look for a hot surface ignitor or spark. A cracked ignitor or failed spark module needs replacement.
- Inspect flame and burners
- Clean dirty burners carefully. Yellow flame or soot means combustion issues.
- If you see rolling flames or smell strong gas, shut off the unit and call a pro.
- Test safety switches and limit switches
- High-limit switches and flame rollout switches can trip and keep the furnace off.
- Reset only after you understand the cause. Repeated tripping means ventilation or heat exchanger problems.
- Evaluate the control board and LEDs
- Note blink codes. Many Rheem boards flash codes for flame lockout, pressure switch faults, or limit trips.
- Turn power off and reseat wire harnesses; corrosion can cause intermittent faults.
- Check the pressure switch and inducer motor
- A blocked inducer vent or failed pressure switch prevents ignition.
- Clean venting and ensure inducer runs smoothly.
- Inspect the gas valve and supply
- Confirm gas supply is on and other gas appliances work.
- A faulty gas valve shows no valve activation when the system calls for heat.
- Document findings and decide on repair or callout
- If the issue is a simple clean or filter change, proceed. For gas valve, heat exchanger cracks, or persistent safety trips, call a licensed HVAC technician.
I once replaced a failing pressure switch on a Criterion II after ruling out vent blockages. The unit ran quietly afterward. Small wins like that are satisfying and instructive.
Diagnostic codes and LED patterns (how to read them)
Reading the control board helps with Rheem Criterion Ii Gas Furnace Troubleshooting. Codes vary by board but follow patterns.
- Rapid flashes followed by pauses often indicate specific fault numbers. Count flashes.
- One flash repeated may mean limit switch fault. Two flashes may point to pressure switch.
- Long steady blink or no LEDs can mean power or board failure.
- Record the pattern and consult the manual or label inside the furnace for mapping.
If you can’t find a manual, take a clear photo and share it with a technician. Many issues resolve faster with a code.
Parts that commonly fail and replacement tips
Knowing weak points cuts diagnostic time. These parts often show up in Rheem Criterion Ii Gas Furnace Troubleshooting.
- Air filter
Cheap to replace and often the culprit for airflow problems. - Ignitor or pilot assembly
Hot surface ignitors are fragile and fail with age. - Pressure switch and hose
Hoses get clogged; switches fail or stick. - Control board
Heat, corrosion, or voltage spikes can damage boards. - Gas valve
Mechanical wear causes intermittent gas flow. - Blower motor and capacitor
Motors age and capacitors fail, causing running issues.
When replacing parts, match model numbers. Use OEM parts for reliability. Take photos of wiring before disconnecting. If you’re unsure about gas components or the heat exchanger, hire a pro.
Maintenance tips to prevent future problems
Routine care reduces the need for Rheem Criterion Ii Gas Furnace Troubleshooting. Make these tasks regular.
- Replace or clean filters every 1–3 months.
- Schedule annual professional tune-ups in fall.
- Keep venting and intake areas clear of debris and snow.
- Lubricate blower bearings if the motor requires it.
- Inspect the combustion chamber and burners for soot or buildup.
- Check thermostat placement and settings to avoid short cycles.
I recommend a checklist on your phone. A short annual checklist saved me a weekend emergency call.
PAA-style questions (People Also Ask)
How do I reset my Rheem Criterion II furnace?
- Locate the furnace switch or breaker and turn it off for 30 seconds, then back on. Some units also have a reset button on the control board; use it only once to avoid repeated lockouts.
Why does my Rheem Criterion II keep short cycling?
- Short cycling most often comes from restricted airflow, dirty filter, or a failing high-limit switch. Verify airflow and replace filters before inspecting switches.
Can I clean the burners myself?
- Yes, you can clean visible surface grime with a soft brush after shutting off power and gas. For deep cleaning or if you see corrosion, call an HVAC technician.
What does a yellow furnace flame mean?
- A yellow flame often signals improper combustion or dirty burners. It can produce carbon monoxide, so stop use and get a professional inspection.
When should I replace the furnace rather than repair?
- Consider replacement when repair cost exceeds 50% of a new unit, the furnace is older than 15–20 years, or the heat exchanger is cracked.
Frequently Asked Questions of Rheem Criterion Ii Gas Furnace Troubleshooting
How do I know if the control board is bad?
A bad control board often shows no LED activity or random faults despite correct power. Visual signs include burn marks or bulging capacitors, and diagnostic checks confirm inconsistent voltages.
Why won’t my pilot stay lit on a Criterion II?
A pilot that won’t stay lit can mean a faulty thermocouple, dirty pilot orifice, or a weak pilot flame. Clean the pilot and replace the thermocouple if needed, or call a pro if the issue continues.
What causes a strong gas smell near the furnace?
A gas smell suggests a leak or a failing gas valve. Shut off gas, ventilate the area, and call your gas provider or a licensed technician immediately—do not operate the furnace.
Can I reset the flame rollout switch myself?
You can reset some rollout switches by pressing a reset button after fixing the underlying cause. If the rollout switch trips repeatedly, stop and call a technician to inspect the heat exchanger and venting.
How often should I schedule professional maintenance?
Schedule maintenance once a year before heating season. Annual checks reduce breakdowns and help with safe, efficient operation.
Conclusion
This Rheem Criterion Ii Gas Furnace Troubleshooting guide equips you with clear steps to diagnose, fix, and prevent common problems. Start with safety and basic checks, use systematic troubleshooting, and document error codes. If the repair involves gas valves, heat exchangers, or repeated safety trips, call a licensed HVAC technician. Take action now: replace dusty filters, note any LED blink patterns, and schedule annual maintenance to keep your furnace running safely and efficiently. Leave a comment with your symptom or photo, or subscribe for more hands-on HVAC tips.
