Payne PG8MAA Error Code Limit Circuit Fault: Limit Circuit Fault

What Does Code Limit Circuit Fault Mean?

Status code 33 on the Payne PG8MAA indicates that the limit switch, draft safeguard switch, flame rollout switch, or blocked vent safety switch (if installed) is currently open. This is an active fault — the furnace detected an unsafe temperature or venting condition and tripped a safety switch. The blower will run for 4 minutes or until the open switch remakes (closes again), whichever is longer.

If the switch stays open for more than 3 minutes, the code escalates to lockout code 13 and the furnace shuts down for 3 hours. If the switch closes within 3 minutes, code 33 continues to flash until the blower shuts off, and the furnace may attempt another heating cycle.

The most common cause is a dirty air filter or restricted ductwork limiting airflow through the furnace. When the blower cannot move enough air, heat builds up in the heat exchanger and the limit switch opens to prevent damage. The flame rollout switch and blocked vent safety switch (BVSS) require manual reset if tripped — they have a small button that must be pressed. If either of these has tripped, it indicates a potentially dangerous condition that warrants professional inspection.

Common Causes

How to Fix It: Check Air Filter and Vents

What You'll Need

• Replacement air filter (same size as current filter)
• Flashlight

Steps

1. Turn off power at the breaker or power switch and shut off the gas supply valve Locate your electrical panel and turn the furnace breaker to OFF. Find the gas shutoff valve on the gas line leading to the furnace and turn it to the closed (perpendicular to the pipe) position. If you smell gas, leave immediately and call your gas company.
2. Locate and inspect the air filter The air filter on the PG8MAA is typically in the blower compartment or the return air duct near the furnace. Slide it out and check it — if it is visibly coated with dust or you cannot see light through it, replace it immediately.
3. Replace the air filter if dirty Install a new filter of the same size. Make sure the airflow direction arrow printed on the filter frame points toward the furnace (toward the blower). A clogged filter is the most common cause of limit circuit faults.
4. Check all return air vents and supply registers Walk through your home and make sure every return air grille and supply register is open and unblocked. Move furniture, rugs, or curtains away from vents. Closing too many registers reduces total system airflow and can trigger overheating.
5. Restore power and gas Turn the gas supply valve back to open (parallel to the pipe). Turn the breaker back ON. The furnace should resume operation once the tripped switch cools down and remakes. If it has already escalated to code 13, the control will auto-reset after 3 hours or you can cycle the power switch to reset.

When to Call a Professional

Contact a licensed HVAC technician if:

• Code 33 returns after replacing the air filter and opening all vents
• The flame rollout switch has tripped (it has a manual reset button — do not repeatedly reset it)
• The blocked vent safety switch (BVSS) has tripped
• You hear unusual noises from the blower suggesting a loose wheel or failing motor
• Code 33 consistently escalates to lockout code 13 despite a clean filter
• The blower runs but produces very little airflow from the supply registers