Fenwal 35-663904-113 Ignition Module

The Fenwal 35-663904-113 Ignition Module is a microprocessor-based 24VAC Hot Surface Ignition (HSI) control designed for precise timing and consistent performance in commercial and residential gas-fired appliances. This Fenwal 35-66 series module integrates a built-in inducer blower relay and pressure switch monitoring, streamlining the combustion sequence by managing the blower and verifying airflow before the trial for ignition (TFI) begins. With a 15-second pre-purge and a 7-second ignition period, it ensures the combustion chamber is cleared of residual gases and the hot surface element reaches optimal temperature for reliable burner light-off. The multi-try ignition logic provides 3 TFI attempts, reducing nuisance lockouts in challenging environments. Technicians can utilize the on-board diagnostic LED for rapid HVAC troubleshooting, while the flame sense test pins allow for direct flame current measurement without breaking the circuit. This unit is built for direct replacement of legacy 35-66 platforms, maintaining critical safety timings and Detect-A-Flame technology for continuous flame supervision.

• Integrated Combustion Blower Relay: Simplifies system wiring by directly controlling the inducer fan and monitoring the airflow switch for safety.
• Microprocessor-Based Precision: Delivers repeatable pre-purge, inter-purge, and TFI timings that do not drift over the life of the control.
• Advanced Diagnostics: The system LED provides specific flash codes to identify airflow faults, flame failures, or internal control errors.
• Enhanced Flame Supervision: Features remote or local flame sensing capabilities with high sensitivity (0.7 µA minimum) to ensure safe operation.
• Non-Volatile Lockout: Ensures the system remains in a safe state following an unsuccessful ignition sequence until manually reset or power-cycled.

What does a steady LED light on the Fenwal 35-663904-113 indicate?
A steady ON condition typically points to an internal microprocessor failure. In this case, the technician should perform a power reset; if the condition persists, the ignition module requires replacement.

Can this module replace a 35-65 series control?
The 35-66 series includes a combustion blower relay which the 35-65 lacks. While they share core HSI control logic, the wiring and terminal configurations (specifically for the blower and pressure switch) must be verified against the appliance schematic.

How do I check the flame signal on this unit?
Use a standard DC microammeter across the flame current test pins. A stable signal above 0.7 µA is required for the control to maintain the gas valve circuit.

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Disclaimer: While we strive for 100% accuracy, product data and specifications are subject to change. Please contact our team to confirm compatibility or technical details before purchasing.