Honeywell Gas boiler control unit S4565BF1088B

The Honeywell S4565BF1088B is a gas boiler control unit designed for use in residential central heating systems, combined boilers, and water heaters with automatic ignition. It operates with a supply voltage of 220–240 V AC and is compatible with gas regulators from the VK41 series. This control unit ensures safe ignition and flame monitoring for the main burner, and it supports systems with pilot burner ignition. It is an OEM equivalent for part numbers 39816360 and 36506940, and fits Ferroli PEGASUS 23-32-45-56 boilers.

When selecting a control unit of this type, verify the supply voltage (220–240 V AC) and the specific gas regulator series it is designed to work with (e.g., VK41). Ensure the unit's ignition system type (pilot burner or spark) matches the boiler's configuration. The control unit connects via a Molex 3003 connector and includes blade terminals for high voltage spark and flame sensing. Always compare the original part number or OEM equivalent to confirm compatibility before installation.

Common failure modes for this type of control unit include failure to ignite, intermittent flame loss, or lockout requiring manual reset. When the unit fails, the boiler may not start, or it may shut down shortly after ignition. Check for proper voltage supply, secure electrical connections, and correct flame sensing rod positioning. If the unit locks out, wait at least 15 seconds before attempting a reset.