Rheem R96VA0702317MSA Error Code 22: Main Limit Open

What Does Code 22 Mean?

Error code 22 on the Rheem R96V means the main high-limit switch has opened because the temperature inside the heat exchanger has exceeded its safe threshold. This is a critical safety fault — gas heating is disabled, but cooling and fan modes still work.

The main limit switch is a safety device that monitors the temperature of the air passing through the heat exchanger. When airflow is restricted, heat builds up inside the furnace instead of being distributed through your home. Once the temperature exceeds the limit switch's setpoint, it opens the circuit and shuts down the gas valve. The furnace will attempt to restart once the limit switch cools down and closes again.

If the limit stays open for more than 150 seconds, the control board determines the blower motor is not functioning and enters a one-hour hard lockout, displaying fault codes 10 and 61 alternately. The most common cause is a dirty or clogged air filter that restricts airflow through the furnace. Blocked return or supply vents and a malfunctioning blower motor are also common causes.

Common Causes

How to Fix It: Replace the Air Filter and Check Vents

What You'll Need

• Replacement air filter (correct size for your system) 🛒 Find at FiltersFast · 🛒 Find at Amazon
• Flashlight

Steps

1. Turn off electrical power at the breaker or power switch AND shut off the gas supply valve Locate the furnace circuit breaker and flip it to OFF, or use the power switch on or near the furnace. Turn the manual gas shutoff valve to the OFF position (perpendicular to the pipe). If you smell gas at any point, leave the house immediately and call your gas company from outside.
2. Locate and remove the air filter Find the air filter — it is typically located in the return air duct near the furnace or inside the blower compartment behind the lower access panel. Slide the old filter out and note its size printed on the frame.
3. Inspect the old filter Hold the filter up to a light source. If you cannot see light through it, the filter is clogged and is very likely causing the overheating. Even if the filter looks only moderately dirty, replace it as a first troubleshooting step.
4. Install a new filter Insert the new filter with the airflow arrow pointing toward the furnace (in the direction of airflow). Make sure the filter is seated properly with no gaps around the edges.
5. Check all supply and return vents Walk through your home and make sure all supply registers and return air grilles are fully open and not blocked by furniture, rugs, or other objects. Closed or blocked vents restrict airflow and contribute to overheating.
6. Restore power and gas, then test Turn the gas supply valve to ON and restore electrical power. Set your thermostat to call for heat. The furnace should start a normal heating cycle. Allow it to run for at least 15 minutes and verify that warm air is flowing from the supply vents.

When to Call a Professional

Contact a licensed HVAC technician if:

• Code 22 returns after replacing the filter and confirming all vents are open
• The blower motor does not start or runs much slower than normal
• The furnace enters lockout with codes 10 and 61 alternating
• You hear unusual noises from the blower motor area
• The furnace repeatedly cycles on and off in short intervals

✓ Verified against manufacturer service manual — March 2026