Goodman Furnace Open Limit Switch – Meaning, Causes & Fix

What Does Open Limit Switch Mean?

What Causes This Error?

• Dirty or clogged air filter severely reducing airflow across the heat exchanger — the most common cause
• Closed or blocked supply registers reducing total system airflow and causing overheating
• Blocked or collapsed return air duct starving the blower of air
• Failed blower motor, bad blower capacitor, or failed blower control board — no air moves across the heat exchanger
• Dirty blower wheel clogged with dust and debris, unable to move enough air
• Oversized furnace short-cycling and overheating the heat exchanger on short cycles
• Cracked heat exchanger causing abnormal airflow patterns and overheating — a serious safety issue posing a carbon monoxide risk
• Faulty limit switch tripping open at a temperature below its set point

How to Fix Open Limit Switch

1. 1

   Turn off power to the furnace and replace the air filter. At the breaker or furnace disconnect, turn off power to the furnace. Locate the air filter (typically in the return air duct or blower compartment), check its condition, and replace it with a clean filter of the correct size if it's dirty. A dirty filter is the most common cause of an open limit switch.

2. 2

   Open all supply and return registers. Walk through the home and confirm all supply registers are open and unobstructed (not covered by furniture, rugs, or curtains), and that all return grilles are clear. Closing registers to save energy is a common cause of furnace overheating.

3. 3

   Restore power and observe a heating cycle. Replace the furnace filter access door, restore power, set the thermostat to call for heat, and observe the furnace. If the air filter and registers were the cause, the furnace should complete a normal heating cycle without the limit switch tripping.

4. 4

   Check the blower wheel if accessible. If the limit switch still trips after a clean filter and open registers, the blower wheel may be clogged. With power off, remove the blower compartment door and inspect the blower wheel for dust and debris; clean it with a stiff brush and vacuum if visibly dirty (a job often best left to an HVAC technician).

5. 5

   Verify the blower motor runs during the heating cycle. With power on and a heat call active, confirm the blower motor starts and runs smoothly at the correct speed. If the blower doesn't start, hums, or runs slowly, the blower motor, blower capacitor, or blower control board has failed and needs replacement.

6. 6

   Call a licensed HVAC technician if the open limit error recurs. If the limit switch continues to trip after replacing the filter, opening all registers, and confirming the blower runs, call a licensed HVAC technician. The cause is likely a failed blower, a dirty blower wheel needing professional cleaning, a faulty limit switch, an oversized furnace, or a cracked heat exchanger — all requiring professional diagnosis, and a cracked heat exchanger poses a carbon monoxide risk.

When to Call a Professional

Can You Still Use the Device?

A Goodman furnace displaying an open limit switch error will not produce heat — the control board shuts off the gas valve as a safety measure, so the furnace will not produce heat until the overheating condition is resolved. The furnace's blower will typically continue to run on high speed to cool the heat exchanger. The furnace may retry a few times before locking out entirely and requiring a power cycle to reset. Heating calls will not produce heat until the underlying airflow or component issue is resolved.