Tank Integrity: Prevents internal vacuum build-up to protect against tank siphoning and structural implosion

Industrial-Grade Durability: Engineered to resist fatigue in high-demand HVACR environments

Using an incorrectly sized diaphragm will result in immediate seal failure and zero stroke control

making this an essential OEM replacement part for technicians restoring system performance to factory specifications

and air handling units that require efficient mixing or diverting

Nordyne 917178A Control Board Els PW 17895 Tank Integrity: Prevents internal vacuumThe Nordyne 917178A Defrost Control Board is the official OEM replacement module designed to restore the automated defrost logic in residential split system heat pumps. This unit is a direct fit successor to the obsolete Nordyne 621579 and various older 1084 series boards, ensuring a seamless interface with existing 24V control circuits and sensor leads. As a veteran grade heat pump defrost control, it utilizes precise temperature monitoring at the