Carrier Furnace Code 25: What It Means & How to Fix It
Compiled & reviewed by Nikolai Tsyrenov · Updated 2026-06-25 · confidence: high
What does Carrier furnace code 25 mean?
Model-selection or setup error — the control board doesn't have a valid model configured (appears on variable-speed boards such as the Carrier 58MVP/58MVC). Most often caused by The model plug (PL4) is missing or incorrect with no valid model in memory (common after a replacement board is installed without the model plug).
What Carrier furnace code 25 means
Model-selection or setup error — the control board doesn't have a valid model configured (appears on variable-speed boards such as the Carrier 58MVP/58MVC).
Common causes
The model plug (PL4) is missing or incorrect with no valid model in memory (common after a replacement board is installed without the model plug)
A setup/configuration DIP switch is positioned improperly
Two different furnace models were twinned together
Note: this code is on variable-speed control boards; it is not present on all Carrier/Bryant models
Homeowner-safe steps to try
This is a control-board configuration error, not something a homeowner can safely correct — it almost always follows a service or board replacement
Confirm with whoever last serviced the furnace whether the model plug and setup switches were configured
Turn the system off and contact your installer/technician rather than attempting board configuration
When to call a licensed HVAC technician
If the basic checks below don't clear the code, the fault recurs, or anything involves the gas valve, burners, flame sensor or wiring, stop and book a licensed HVAC technician. Repairs to the combustion or gas system are not DIY.
⚠️ Safety first. Gas furnaces burn fuel and produce combustion gases. If you ever smell gas (a rotten-egg or sulfur odor), hear hissing, or your carbon-monoxide alarm sounds, do not touch light switches, thermostats, or the furnace — leave the home immediately and call your gas utility's emergency line or 911 from outside. Homeowners should limit themselves to simple, safe steps: setting the thermostat, checking and replacing the air filter, confirming the furnace switch and breaker are on, keeping supply registers and return grilles open, and clearing snow, ice, or debris from outdoor vent and intake terminations. Never bypass, jumper, or reset safety switches (limit, flame-rollout, or pressure switches), never open the gas valve or burner compartment, and never attempt combustion, electrical, or control-board repairs yourself. Error codes point toward a problem but are not a substitute for proper diagnosis — when in doubt, turn the system off and call a licensed HVAC technician. Keep working carbon-monoxide detectors on every level of your home.
When to call a pro: Call the installing or a licensed HVAC technician — code 25 means the board needs the correct model plug and/or setup switches configured to the equipment.
Carrier furnace code 25 FAQ
What does Carrier furnace code 25 mean?
Model-selection or setup error — the control board doesn't have a valid model configured (appears on variable-speed boards such as the Carrier 58MVP/58MVC).
What causes Carrier furnace code 25?
Common causes: The model plug (PL4) is missing or incorrect with no valid model in memory (common after a replacement board is installed without the model plug); A setup/configuration DIP switch is positioned improperly; Two different furnace models were twinned together; Note: this code is on variable-speed control boards; it is not present on all Carrier/Bryant models.
Can I fix Carrier furnace code 25 myself?
You can safely try: This is a control-board configuration error, not something a homeowner can safely correct — it almost always follows a service or board replacement; Confirm with whoever last serviced the furnace whether the model plug and setup switches were configured; Turn the system off and contact your installer/technician rather than attempting board configuration. Call the installing or a licensed HVAC technician — code 25 means the board needs the correct model plug and/or setup switches configured to the equipment.
Sources: manualslib.com · shareddocs.com. General information for homeowners, not professional advice — confirm against your furnace's manual and a licensed technician.