Control Boards

Voomi Supply carries HVAC control boards for furnaces, heat pumps, air conditioners and refrigeration equipment, including furnace, ignition, defrost, fan, display, heater, power supply and water control boards from Goodman, Rheem, Carrier, International Comfort Products and Nortek. A control board is the circuit board that runs a unit's operating sequence: it reads the thermostat call and the safety inputs, then switches components such as the inducer, igniter, gas valve and blower in the right order. Every order ships with Voomi's 30-day return policy and free help matching a board to your equipment.

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Types of Control Boards

Board type

What it does

Browse

Furnace and ignition boards

Run the furnace sequence: inducer, igniter, gas valve and blower, with the safety switches checked at each stage

Furnace control boards and ignition control boards

Defrost boards

Used on heat pumps. They read the coil sensor and, during defrost, switch the reversing valve to cooling, shut off the outdoor fan and send 24V to the backup heat

Defrost control boards

Fan boards

Control the fan or blower circuit

Fan control boards

Display, heater, power supply and water boards

Specialized boards, each in its own subcategory; match them by the part number of the equipment

Display, heater, power supply and water boards

Refrigeration controllers

Universal refrigeration controllers and defrost kits with a thermostat sensor, for coolers and freezers

Shown in the product grid of this collection

Furnace Control Boards Explained

These boards are designed to manage furnace operations, controlling ignition, blower motors, and safety features to keep your home warm and safe. The table shows the typical sequence on a modern gas furnace. Exact timings vary by model, so check the service manual.

Stage

What the board does

Typical timing

Call for heat

Confirms the safeties are normal after the thermostat closes W to R

Not timed

Inducer pre-purge

Starts the inducer to clear gases and establish draft

10 to 60 seconds

Pressure switch proof

Waits for the switch to close; retries or locks out if it does not

Varies by model

Igniter warm-up

Heats a hot surface igniter, or sparks at the burner

10 to 30 seconds

Gas valve opens

Energizes the valve for the ignition trial

4 to 7 seconds

Flame proof

Reads the flame sensor; shuts gas off and retries if flame is not proven

2 to 5 retries before lockout; sensor signal 2 to 6 microamps DC

Blower on delay

Starts the blower after the heat exchanger warms up

30 to 90 seconds

Blower off delay

Keeps the blower running after the call ends to extract residual heat

60 to 120 seconds

How a Defrost Control Board Works

Function

Detail

Starting defrost

A coil sensor reads coil temperature and sends it to the board, which decides when to enter defrost. Some boards also have a timed defrost setting.

During defrost

The board switches the reversing valve to cooling, which sends hot discharge gas to the outdoor coil, shuts off the outdoor fan and sends 24V on the white wire to energize indoor backup heat.

Ending defrost, Carrier example

Defrost ends after 10 minutes or when the defrost thermostat opens at about 65 degrees, whichever comes first.

Ending defrost, Trane example

The board ends defrost based on its sensors, and an average defrost lasts around 6 minutes. These boards do not have adjustable 30, 60 or 90 minute settings.

Reading Furnace Fault Signals

A board that locks out usually flashes a diagnostic code. Codes differ by model, so use the code chart in the service manual. These are common fault groups and what to check first.

Fault

What it usually means

What to check

Pressure switch open

The inducer runs, but the switch never proves

Venting, condensate, hoses and inducer ports

Ignition lockout

Ignition failed after multiple trials

Igniter, gas supply, grounding and the board

Flame sensed with gas off

A stuck gas valve, a shorted sensor or stray flame

Gas valve, sensor wiring and burner area

Limit or rollout open

Overtemperature or unsafe combustion

Airflow and the heat exchanger, before resetting

Polarity or neutral fault

Reversed line and neutral, or a poor ground

Line wiring and the equipment ground

How to Pick the Right Control Board

Choosing the correct control board requires checking compatibility with your equipment's brand and model to guarantee seamless operation. Use this checklist.

Match

What to compare

Part number

The number printed on your existing board, and the part numbers named on the listing

Equipment brand and model

The model on the equipment nameplate

Board function

Furnace, ignition, defrost, fan, power or display, since these boards are not interchangeable

Connectors

The plug layout and wire harness of the old board against the listing photos

Browse more boards in HVAC control & circuit boards, or find the part by symptom in the guide above. For heating boards, see furnace control boards.

Frequently Asked Questions

A furnace control board runs the heating sequence. After the thermostat calls for heat, it confirms the safety switches, starts the inducer, warms the igniter, opens the gas valve for a short ignition trial, checks the flame sensor, and then starts the blower after a delay of roughly 30 to 90 seconds. When the call ends it closes the gas valve and keeps the blower running for about 60 to 120 seconds. Timings vary by model. Browse furnace control boards to find your part.

Signs of a faulty control board include inconsistent heating, continuous fan operation, or failure to ignite the furnace. Checking the diagnostic light for error codes can also help pinpoint the problem. Codes differ by model, so use the chart in the service manual. Many faults come from the system rather than the board, such as a blocked vent, a dirty flame sensor or poor airflow, so confirm those before you replace the board.

Control boards can fail due to power surges, overheating, age-related wear and tear, moisture exposure, or improper wiring. Regular maintenance and proper installation can help prevent most issues.

A defrost control board manages the defrost cycle on a heat pump. It reads the coil sensor to decide when to defrost, then switches the reversing valve to cooling to send hot gas to the outdoor coil, shuts off the outdoor fan and energizes the indoor backup heat so the space does not cool down. On a Carrier board, defrost ends after 10 minutes or when the defrost thermostat opens at about 65 degrees. See our defrost control boards.

A board locks out after a preset number of failed ignition attempts, commonly 2 to 5 retries, and it flashes a diagnostic code. Likely causes are the igniter, the gas supply, grounding or the board itself. Check the code in the service manual first, and have a licensed technician check gas and combustion safety.

Whether to replace the board or the furnace depends on the furnace's age and condition and on any other repairs it needs, so compare the cost of the board with the state of the whole system.

While experienced DIYers may attempt to replace the control board, incorrect installation can lead to further damage or void the warranty. It's recommended to consult with a professional HVAC technician to ensure proper installation.