Trane Heat Pump: 4TWB, 2TWR, 4TWR Re: Defrost Problem / Frozen Outdoor Coil The outdoor unit becomes completely covered in thick, white ice. Qty Possible Causes: Bad Coil Sensor 1 Mis-Located Coil Sensor Inoperative Condenser Fan Motor Bad Defrost...

Demand Defrost Control There are two versions of the defrost control board: Mnemonic No. 07255 = PSC Motor Mnemonic No. 07256 = ECM Motor The demand defrost control measures heat pump outdoor ambient temperature with a sensor located outside the outdoor coil. A second sensor located on...

Make: Trane Model or Series: 4TWR Type: Heat Pump Problem Description: Contactor won't energize Observed Symptoms: 24Volts on "Y" but never starts contactor Solution: Found bad high pressure switch Additional Information: Checked for and had 24V at Yellow wire on defrost board...

Trane Heat Pump: 4TWR Re: Compressor Kicks On and Off in Cooling The compressor and condenser fan motor cycle on and off rapidly. Often accompanied by burnt compressor contactor points from excessive cycling. ► The Low and High Pressure switches are wired in series with the "Y" output...

Trane Heat Pump: 4TWR3 Re: Not Defrosting / Frozen The 4TWR3 models 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. Qty Possible Causes: Bad Liquid Line Sensor ...

Trane Heat Pump: 4TWR3 Re: Flashing Code 4 Code 4 = 4 trips of the Low Pressure Control 1st LPCO trip = 15 min. Soft lockout 2nd LPCO trip = 30 min. Soft Lockout 3rd LPCO trip = 4 hour (cooling), 18 hour (heating) Soft Lockout 4th LPCO trip = Hard Lockout Qty Possible Causes: ...