York Heat Pump: YMA Re: Not Defrosting / Frozen These units use a Demand Defrost control board. The board uses an Ambient (outdoor) Sensor and Liquid Line Sensor to determine the proper conditions for defrost to occur. ♦ VERY IMPORTANT! The YMA heat pump was originally produced with R-22...

York Heat Pump: YMA Re: Replacement Demand Defrost Control Board - S1-33101975102 INSTALLATION Power off unit totally - 240V & 24V Pull unit disconnect. Disconnect high voltage power to air handler Record positions and colors of original wiring. Remove old defrost control...

York Heat Pump: YMA **INCOMPLETE** Re: Outdoor Unit Starts Then Shuts Off The contactor on the outdoor unit pulls-in and the unit starts running, but shuts off after a short runtime. Qty Possible Causes: 1 Bad Hi Pressure Switch Bad Low Pressure Switch ...

Heat Pump: YMA Re: Contactor Won't Energize Thermostat calling for heating or cooling, but the contactor on the outdoor unit doesn't pull-in. No Compressor Operation No Outdoor Fan Operation Qty Possible Causes: 1 Safety Lockout Bad Hi Pressure Switch ...