Ruud U802VA050317MSA Error Code A022_F: Main Limit Switch Open (Active)
What Does Code A022_F Mean?
Code A022_F on the Ruud U802VA indicates that the main high-temperature limit switch is persistently open due to sustained overheating. The 'A' prefix means this is an active, ongoing condition — not a one-time trip. If the limit circuit stays open for more than 150 seconds, the control declares a 'dead blower' condition, meaning the blower motor is likely not moving enough air.
This is a more serious version of the transient T022_F code. While a transient limit trip may clear on its own, an active code means the furnace cannot cool itself down. The control may enter a one-hour lockout to prevent further overheating and potential damage to the heat exchanger.
The most common DIY-addressable cause is severely restricted airflow from a dirty filter or blocked vents. However, because this is a persistent condition, there is a higher likelihood that the blower motor has failed or is running too slowly. Prompt attention is needed — continued overheating can crack the heat exchanger, which is a costly and potentially dangerous condition.
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Severely restricted airflow (dirty filter, blocked ducts) | Most common | ✓ DIY fix → |
| Blower motor not running (dead blower) | Common | ✗ Call a pro → |
How to Fix It: Replace the Air Filter and Restore Airflow
What You'll Need
- Replacement air filter (correct size for your system) 🛒 Find at FiltersFast · 🛒 Find at Amazon
- Flashlight
Steps
- 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 gas shutoff valve to the OFF position (perpendicular to the pipe). If you smell gas at any point, leave the area immediately and call your gas company.
- Check and replace the air filter Remove the air filter from the return air duct or furnace filter slot. If it is dirty, clogged, or has not been changed recently, replace it with a new filter of the correct size. Make sure the airflow direction arrow on the new filter points toward the furnace.
- Verify all supply and return vents are open and unblocked Walk through every room and ensure all supply registers and return air grilles are fully open. Remove any furniture, curtains, or rugs blocking the vents. Check that the return air pathway is completely unobstructed.
- Listen for the blower motor With the power still off, look through the blower access panel. Check for excessive dust on the blower wheel. When you restore power, listen carefully — if you do not hear the blower motor running at all, or if it sounds strained or unusually quiet, the motor may have failed. A dead blower motor requires professional replacement.
- Restore gas and power, then test Turn the gas supply valve to ON and restore electrical power. Cycle the power (off for 30 seconds, then back on) to clear the lockout. Set the thermostat to call for heat and observe whether the blower motor starts and runs at normal speed.
When to Call a Professional
Contact a licensed HVAC technician if:
- The blower motor does not start or makes grinding/humming noises without spinning
- Code A022_F returns after replacing the filter and confirming all vents are open
- The furnace enters the dead blower lockout (limit open for more than 150 seconds)
- You hear the burners ignite but feel no air coming from the supply vents
- The blower wheel is visibly damaged, loose, or excessively dirty
Sources
✓ Verified against manufacturer service manual — March 2026