Goodman GMVM970803BN Error Code E3: Open High Limit Switch

What Does Code E3 Mean?

An E3 code on the Goodman GMVM970803BN indicates the primary high-limit switch has opened. This temperature-sensitive safety device is mounted on the partition panel near the heat exchanger compartment. When temperatures inside the furnace exceed safe operating limits, the switch opens the circuit and shuts down the burners to protect the heat exchanger. The circulator blower continues running to cool the overheated components, but the furnace will not fire, and a ComfortNet thermostat shows "Call for Service" and scrolls "Check Furnace."

The high-limit switch trips when airflow across the heat exchanger is too low, so heat builds up faster than the blower can carry it into the ductwork. On this variable-speed furnace the ECM blower tries to hold its target airflow, but a restriction it cannot overcome pushes heat-exchanger temperature past the limit. A dirty or clogged air filter is the number-one cause, followed by closed or blocked supply and return registers that force the furnace to recirculate the same hot air.

E3 is an airflow problem, which is why it is the one code in this group with safe homeowner steps — replacing the filter and opening registers directly addresses the most common cause. It differs from the pressure-switch codes (E1/E2), which are about combustion venting, and from an E0 lockout, which is about failed ignition. Here the burners were lighting fine; the furnace simply got too hot to run safely.

If a clean filter and open registers do not resolve it, the cause is likely beyond DIY: an ECM blower running at the wrong programmed speed, restrictive or undersized ductwork, or a loose wiring connection. The high-limit switch is an automatic-reset type, so it resets on its own once temperatures fall — but it will keep tripping until the airflow restriction is corrected.

What You'll Notice

• The circulator blower runs continuously (often on high) while the burners stay off and no new heat is made
• The control module displays E3 and a ComfortNet thermostat shows "Call for Service" / "Check Furnace"
• The air filter is visibly dirty or overdue for replacement
• Some supply registers or return grilles are closed or blocked by furniture, rugs, or curtains
• The furnace may run briefly, overheat, shut off the burners, then repeat once the limit resets

Common Causes

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

1. Turn off electrical power at the breaker or switch and shut off the gas supply valve Locate the furnace circuit breaker or the unit's ON/OFF switch and turn it OFF. Turn the gas shutoff valve to the OFF position (handle perpendicular to the pipe). If you smell gas, leave immediately and call your gas company from outside. Do not restore power or gas until you are finished.
2. Check and replace the air filter Remove the air filter from the return duct or furnace filter slot. If it is visibly dirty, clogged, or has not been changed in the last few months, install a new filter of the correct size. Make sure the airflow arrow printed on the filter frame points toward the furnace.
3. Open and unblock all supply and return registers Walk through every room and confirm each supply register and return grille is fully open. Move furniture, rugs, or curtains that cover them. Closed or blocked registers are a leading cause of overheating because they starve the system of return airflow — do not close off vents to unused rooms.
4. Clear any obvious obstruction at the furnace air openings With the power still off, make sure nothing (boxes, stored items, insulation) is blocking the return-air opening or the supply plenum at the furnace itself. Do not adjust blower speed, open the gas train, or touch any wiring — if the blockage is not something you can simply remove by hand, stop and have a technician evaluate it.
5. Restore gas and power, then run a full heating cycle Turn the gas valve back ON (handle parallel to the pipe) and turn the breaker or switch ON. The high-limit switch is automatic-reset and should clear once temperatures normalize; you can also cycle power off for about 30 seconds and back on. Set the thermostat to call for heat and watch a complete cycle.

When to Call a Professional

Contact a licensed HVAC technician if:

• E3 returns after replacing the filter and confirming all registers are open
• The blower motor does not seem to run at full speed or makes unusual noises
• The blower wheel is loose, damaged, or heavily caked with dust
• You suspect the ductwork is undersized or poorly routed for the furnace capacity
• The code keeps recurring even with regular filter changes

✓ Verified against manufacturer service manual — March 2026