Disconnect power and use a multimeter to check the resistance across the leads

this push-button HVAC controller is specifically designed with a dual relay type that supports sequencing relays

the FUS0823 is the direct replacement for S8402-091

listen for the reversing valve shifting

designed to meet the same technical specifications

Reznor 177633 Pressure Switch Els PW 17895 Disconnect power and use aThe Reznor 177633 Pressure Switch is a critical OEM replacement part designed for precision monitoring within commercial gas heating systems. Engineered for unit heaters and duct furnaces, this combustion air pressure switch kit is factory calibrated to a 0. 50" W. C. setpoint (water column). The Reznor 177633 ensures safe ignition sequences and reliable venting verification by detecting proper differential pressure before allowing the gas valve to