Fenwal 35-665535-011 Ignition Module

The Fenwal 35-665535-011 Ignition Module is a high-performance, microprocessor-based 24 VAC hot surface ignition control designed for heavy-duty gas-fired equipment, including boilers, furnaces, and water heaters. Engineered to manage the full combustion sequence, this module integrates safe start logic, flame sensing, and blower relay control into a single, compact unit. As a three-try ignition model, it provides improved reliability in demanding environments by allowing multiple attempts to prove flame before entering a safe lockout state. With a precise 15-second pre-purge and a 4-second trial-for-ignition (TFI) period, it ensures consistent burner operation and safety, while the diagnostic LED simplifies field troubleshooting by providing instant fault code feedback. This direct OEM replacement is built to withstand operating temperatures from -40°F to 176°F, making it a rugged choice for service technicians handling natural gas, LP, or manufactured gas systems requiring dependable HSI control and airflow monitoring.

• Microprocessor Accuracy: Provides repeatable timing for pre-purge, inter-purge, and ignition cycles, reducing call-backs for intermittent failures.
• Advanced Diagnostics: Features an on-board LED indicator for rapid fault identification, including airflow faults and ignition lockout status.
• Flame Sensing Technology: Offers full-time monitoring with a 0.7 microamp minimum sensitivity for local or remote flame sensing configurations.
• Multi-Try Reliability: The 3-try ignition sequence increases the success rate for combustion in cold starts or varied fuel conditions.
• Versatile Compatibility: Designed as a field-selectable solution for various 24V gas-fired appliances with robust contact ratings for gas valves and blower motors.

• How do I reset the module after an ignition lockout? Lockout can be cleared by cycling the thermostat or removing the 24 VAC input power for at least 5 seconds.
• What does a flashing LED on the control board indicate? The diagnostic LED uses specific flash patterns to identify issues such as erroneous flame signals, airflow pressure switch malfunctions, or internal control failures.
• Is this module compatible with LP gas systems? Yes, the Fenwal 35-66 series is rated for use with natural, propane (LP), and manufactured gas.

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.