a functioning P043800 should produce approximately 750mV under open-circuit conditions (disconnected from the valve) while heated by the pilot flame

reducing pressure drop across the S21 series valve assembly

if the vacuum is sufficient but the switch remains open

contractor-grade power venter motor kit engineered to restore precise draft control in residential and commercial heating systems

Maintenance Optimized: The slider bar contact design reduces pitting and carbon buildup

Lochinvar & A.O. Smith 100233678 Fan Gasket 320819-301 a functioning P043800 should produceAs a field technician, you know that maintaining a precise seal in the combustion assembly is non negotiable for system safety and peak thermal efficiency. The Lochinvar & A. O. Smith 100233678 Fan Gasket is a critical OEM component engineered to provide a high temperature seal between the combustion fan and the blower transition or venturi assembly. Designed specifically for use in Lochinvar Knight boilers and high efficiency A. O. Smith commercial