I have been trying to resolve a problem of inadequate heat in a 2000 Taurus with the Vulcan engine. I have eliminated the simple things, thermostat, water pump, blend door actuator, cooling system flush, heater core flush. There is a temperature change when one turns the temperature control knob from stop to stop, but the difference is minimal. A mechanic diagnosed the problem as being a broken part in the heater case, (an $1100 repair estimate) which he says generated a diagnostic code. I have some doubt about his claim. I'll invest some time before I give him half of the value of the car to prove his claim. If you have any ideas, I will give them a try.