Fenwal 35-704903-001 Control

The Fenwal 35-704903-001 is a microprocessor-based Direct Spark Ignition (DSI) control designed for 120VAC gas-fired equipment. This single-try ignition module features a 4-second Trial for Ignition (TFI) period, offering precise timing for commercial heating and industrial process applications. Engineered for reliability in demanding environments, the Fenwal 35-70 series utilizes specialized circuitry to monitor the flame via flame rectification, ensuring safe operation by closing the gas valve if no flame is detected. This specific configuration operates without a pre-purge (NoPP) cycle, facilitating immediate ignition sequences. It serves as a critical component for contractors performing Fenwal ignition control replacement, providing a direct fit for systems requiring 120V power input and diagnostic LED capabilities. For technicians troubleshooting HVAC furnace control boards, this module offers robust electromagnetic interference (EMI) protection and consistent performance across varying temperature ranges.

• Precise Timing: Features a fixed 4-second TFI for efficient burner lighting without extensive delay.
• Direct Spark Technology: Eliminates the need for a standing pilot, increasing overall system efficiency.
• Industrial Durability: Built with a conformal coating to protect internal circuitry against moisture and vibration.
• Simplified Integration: The 120VAC input and standard terminal layout allow for streamlined field installation.
• Safety Monitoring: High-sensitivity flame sensing circuit prevents hazardous gas buildup during ignition failure.

How do I troubleshoot a lockout on the Fenwal 35-704903-001?
If the module fails to sense a flame within the 4-second TFI, it enters a lockout state. Check the flame rod for carbon buildup, ensure proper grounding, and verify the 120V power supply polarity. Resetting the control requires cycling the thermostat or main power.

Can this ignition control replace a multi-try module?
This specific model is a single-try (1 Try) unit. While it may fit the physical footprint, the sequence of operation must match the appliance manufacturer's original specifications for safety compliance.

Does this control support pre-purge cycles?
No, this model is a (NoPP) variant, meaning it initiates the spark and gas valve energization immediately upon receiving a call for heat.

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.