When I turn on heater it only blows cold air

Check to see if both heater hoses are hot if they are then it may be a control problem or actuator not getting power or vacuum. If this is auto temp control then it will have to be scanned to see what is wrong with it. Here is a tip I found: type v6  Flow to heater core can be checked by removing water control valve inlet hose and pour water down into it.  Remove the smaller hose on the front of the water pump
housing to do this.  The valve cannot be bench tested!
There is no blend door with this system.  Jaguar website is no help.  Check out lincoln LS in mitchell for better information.