Carrier Furnace Control Board Manual

The Carrier Furnace Control Board is the central electronic component that manages and coordinates all furnace operations, including ignition sequences, fan control, safety monitoring, and communication with thermostats. This manual covers installation, operation, troubleshooting, and maintenance procedures for Carrier furnace control boards across various models. Below are key sections for safety, features, installation, setup, operation, and troubleshooting.

1. Features at a Glance 2. Installation 3. First-Time Setup 4. Specifications 5. Controls and Settings 6. Connecting Components 7. Operation Modes 8. Diagnostic Features 9. Maintenance & Care 10. Regulatory Information 11. Troubleshooting

Features at a Glance

Key components: Main control board, LED status indicators, terminal connections, fuse protection, integrated diagnostics.

FeatureDescription
LED Status IndicatorsVisual fault codes and operational status
Thermostat TerminalConnection for thermostat control wires
Pressure Switch InputSafety monitoring for venting system
Igniter ControlManages hot surface igniter operation
Gas Valve ControlRegulates gas valve opening and closing
Blower Motor ControlControls indoor blower speed and timing
Limit Switch InputSafety monitoring for overheating
Flame Sensor InputVerifies burner ignition
Fuse Protection3A or 5A fuse for circuit protection
Diagnostic CodesFlash codes for troubleshooting

Installation

Ensure power is disconnected before installation. Follow proper safety procedures.

  1. Disconnect power: Turn off furnace power at main disconnect and circuit breaker.
  2. Remove old board: Disconnect all wires and mounting screws from existing control board.
  3. Install new board: Mount new control board using provided screws and brackets.
  4. Connect wiring: Reconnect all wires to corresponding terminals on new board.
  5. Restore power: Turn power back on and verify proper operation.

WARNING! High voltage present. Only qualified technicians should perform installation. Follow all local electrical codes.

First-Time Setup

After installation, perform initial setup and testing procedures.

  1. Power up sequence: Restore power and observe LED status lights.
  2. System check: Verify all safety controls are functioning properly.
  3. Thermostat calibration: Ensure thermostat communication is established.
  4. Test operation: Initiate heating cycle to verify proper ignition and operation.
  5. Monitor diagnostics: Check for any error codes during initial operation.

CAUTION! Always verify gas connections for leaks before operating furnace.

Specifications

Controls and Settings

Control board manages all furnace functions through integrated microprocessor.

LED Status Codes: Steady green = normal operation; flashing codes indicate specific faults.

Ignition Sequence: Prepurging, igniter warm-up, gas valve opening, flame verification, main burner operation. Fan Control: Delayed fan-on after ignition; continuous fan during heating; post-purge fan operation. Safety Monitoring: Continuous monitoring of limit switches, pressure switches, flame sensor. Diagnostic Mode: Access through specific jumper settings or thermostat commands.

Connecting Components

Proper wiring connections are critical for safe and efficient operation.

  1. Thermostat connections: R (24V), W (heat), G (fan), C (common)
  2. Pressure switch: Normally open switch for venting verification
  3. Limit switches: High temperature safety cutoffs
  4. Gas valve: 24V control for gas flow regulation
  5. Igniter: Hot surface igniter control circuit
  6. Blower motor: Multi-speed control connections
  7. Flame sensor: Flame verification input

Tip: Always reference wiring diagram specific to your furnace model.

Operation Modes

Control board manages various operational modes for efficient heating.

  1. Standby mode: Waiting for thermostat call for heat
  2. Ignition sequence: 30-second prepurge, 17-second igniter warm-up
  3. Heating mode: Main burner operation with blower activation
  4. Fan only mode: Continuous air circulation without heating
  5. Safety shutdown: Automatic shutdown if faults detected
  6. Lockout mode: System lockout after multiple failed ignition attempts
  7. Diagnostic mode: Service mode for troubleshooting and testing

WARNING! Never bypass safety controls or attempt to operate furnace with known faults.

Diagnostic Features

Integrated diagnostic system provides fault codes via LED flashes for quick troubleshooting.

LED Flash PatternFault Description
1 FlashIgnition failure
2 FlashesPressure switch fault
3 FlashesLimit switch open
4 FlashesFlame sensed with gas valve off
5 FlashesBlower fault
6 FlashesGas valve circuit fault
7 FlashesPressure switch stuck closed

Maintenance & Care

Regular maintenance ensures optimal performance and longevity.

  1. Annual inspection: Have qualified technician inspect control board and connections
  2. Clean connections: Ensure all terminal connections are clean and secure
  3. Check fuse: Verify fuse is intact and proper rating
  4. Monitor operation: Listen for unusual sounds during operation
  5. Keep area clean: Ensure furnace area is free from dust and debris

CAUTION! Always disconnect power before performing any maintenance.

Regulatory Information

UL Listed and CSA Certified. Complies with ANSI Z21.47 standards for gas-fired central furnaces. Manufactured in accordance with ISO 9001 quality standards. Copyright © 2025 Carrier Corporation. All rights reserved. Carrier is a registered trademark of Carrier Global Corporation. For technical support, visit www.carrier.com or contact 1-800-CARRIER.

Troubleshooting

SymptomPossible CauseCorrective Action
No heatPower loss, thermostat issueCheck circuit breaker, verify thermostat settings, check control board LED
Furnace short cyclingDirty filter, blocked ventsReplace air filter, check for vent obstructions
Blower not runningMotor failure, control issueCheck blower motor, verify control board output
Ignition failureGas supply, igniter faultVerify gas valve operation, check igniter continuity
Lockout modeMultiple fault conditionsReset power, diagnose root cause using LED codes
Error codes flashingVarious fault conditionsReference diagnostic chart for specific flash pattern

Reset Procedure: Turn power off for 30 seconds, then restore power.

Service: 1-800-CARRIER; www.carrier.com

Carrier Furnace Control Board Manual © - All Rights Reserved 2025