2005 Jaguar S-Type

I apologize for the slow response.I have forwarded your question to our Jag tech, he should be with you shortly

Helllo .. thanks for the donation .. much appreciated .. sorry for the delay in the reply .. work commitment's.

When you bypassed the heat function .. did the A/C run cold, as it should, or just blow cool air ??

Heating and Ventilation - Description & Operation
The heating and defrosting system:
controls the vehicle air temperature and, during air conditioning (A/C) operation, reduces the relative humidity of the air inside the vehicle.
delivers heated or cooled air to maintain the vehicle interior temperature and comfort level.
controls the brushless blower motor speed.
allows temperature to be adjusted individually by the driver and the passenger to maintain comfort.
uses a reheat method to provide conditioned air to the passenger compartment. All airflow from the blower motor passes through the A/C evaporator core. Temperature is regulated by reheating a portion of the air and blending it with the remaining cool air to achieve the desired temperature.
blends the air temperature by regulating the flow of engine coolant to separate halves of the heater core. A dual coolant flow valve is used to control the flow of coolant.
The blower motor draws ambient air through the cabin air filter during all system operations except for MAX A/C cooling (when recirculated air is used) and OFF. For additional information, refer to Air Conditioning .