Goodman GMVM970803BN Error Code EF: Auxiliary Input Open

What Does Code EF Mean?

An EF code on the Goodman GMVM970803BN indicates that the auxiliary input circuit on the integrated control module is open. The auxiliary input terminals are designed to accept an external safety device — most commonly a condensate overflow float switch or a secondary limit switch. When nothing is connected to these terminals, a jumper wire must be installed to complete the circuit. If the jumper is missing or a connected safety device has tripped, the control board sees an open safety circuit and refuses to operate.

The most common scenario for this code is a condensate overflow condition. As a condensing furnace, the GMVM970803BN produces liquid condensate during operation that must drain away continuously. If a float switch is connected to the auxiliary input and the condensate drain becomes clogged with algae, debris, or a buildup of mineral deposits, water backs up and triggers the float switch, opening the auxiliary input circuit. This is the safety system working as intended — it shuts down the furnace to prevent water damage.

Less commonly, the jumper wire between the auxiliary terminals may have been accidentally removed during a service call, or wiring to an external safety device may have come loose. In all cases, this code requires a technician to determine what device — if any — is connected to the auxiliary input and address the underlying condition.

Common Causes

When to Call a Professional

Contact a licensed HVAC technician if:

• If a condensate float switch is installed, call a technician to inspect the condensate drain pan and line for standing water — the drain must be cleared and the condensate system verified before the furnace will resume operation
• If no external device is connected, a technician should verify the jumper wire is properly installed between the auxiliary input terminals on the control board

✓ Verified against manufacturer service manual — March 2026