Bergstrom 7787B173090 Heater Control Valve

Bergstrom 7787B173090 Heater Control Valve (also listed as B173090 and KYS173090) is a Bergstrom/KYSOR water valve replacement designed for Thomas Built Buses, and it functions to regulate coolant flow to the heater core to modulate cabin heat. The valve is documented in Bergstrom’s aftermarket catalog as the KYS 173090 water valve (B173090) for Thomas Bus installations, and Thomas’ OEM cross-reference confirms B173090 with OEM NO. KYS173090. In Thomas Bus parts inventories it is commonly cataloged as Water Valve 2499006, aligning with the same part across distributor networks. Some retailer listings describe the unit as a heater valve with 5/8-inch hose connections and cable actuation, consistent with the Thomas Bergstrom heater valve configurations observed in the market. The 7787B173090 designation ties this specific listing to the same heater-control valve family used in Thomas Bus HVAC systems, providing a direct replacement for failed or leaking valves and restoring proper heat control in equipped models.