Fenwal 35-655921-001 Ignition Module

The Fenwal 35-655921-001 is a microprocessor-based 24 VAC Hot Surface Ignition (HSI) Control engineered for precise management of gas-fired appliances. This direct replacement ignition module handles the complete demand sequence, including combustion blower control, flame sensing, and diagnostic monitoring. Designed for systems under 400K BTU, it features a 5-second Trial for Ignition (TFI) and a 5-second ignitor heat-up period to ensure stable combustion. The 35-655921-001 module utilizes DETECT-A-FLAME technology for reliable remote flame sensing and includes a 0-second pre-purge configuration for immediate response in specific furnace, boiler, and water heater applications. The gray Noryl N-190 fire-retardant enclosure provides maximum protection in temperatures ranging from -40°F to +176°F. Integrated LED diagnostics simplify field troubleshooting by indicating lockout conditions and system faults, minimizing downtime for HVAC contractors. This Fenwal 35 Series control is not position-sensitive, allowing for versatile mounting in tight mechanical spaces.

• Enhanced Troubleshooting: On-board diagnostic LED provides instant feedback on fault modes, reducing diagnostic time for field technicians.
• Precise Timing: Microprocessor control ensures repeatable 5-second ignition sequences and consistent heat-up cycles for optimal burner performance.
• Robust Safety: Features safe start logic and continuous flame monitoring to prevent hazardous gas buildup during ignition failure.
• Universal Applications: Compatible with natural, LP, and manufactured gases in commercial and residential gas-fired equipment.
• High Output Ratings: Supports gas valve loads up to 2.0A and hot surface ignitors up to 5.0A at 24 VAC.

How do I resolve a 3-flash LED error code?
A 3-flash signal typically indicates an ignition lockout. This occurs when the module fails to detect a flame signal after the allotted Three Trials for Ignition. Check the gas supply, inspecting the ignitor for continuity, and ensure the burner ground is secure.

Can I test the flame signal on this module?
Yes. Connect a DC micro-ammeter to the FC+ and FC- terminals. A healthy flame current should measure 1.0 µA DC or higher. Alternatively, a voltmeter can be used; each micro-amp of current corresponds to 1.0 VDC.

What should I check if there is no voltage to the gas valve?
Confirm 24 VAC is present at the W terminal. If the HSI element glows but the valve remains de-energized, verify the pressure switch is closing and that the module is not in safety lockout from a previous failed attempt.

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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.