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I have a 2002 Ford Taurus with a 3.0 LTR V-6, OHV (base) engine.  The engine is running at normal temperature and the blowers are working properly but I am getting no heat.  The system blows cool to luke-warm air.  The thermostat and radiator (reservoir) cap are good.  

this is not as simple as it might seem...

just look at the heater hose assembly behind the motor...




the two hoses in the middle connect to the heater core..

the outside ends connect to the motor..  if you have an infrared thermometer.. you can with the engine running.. measure the temp of the coolant flow through the hose .. see if its different..  with the heater fan off.. it should be close to the same.. coming in and going out..   with the heater fan blowing.. it should be different..

if one end is cold..  you might need to check the thermostat ...  that it is actually cycling open and closed again..   if the thermostat is stuck open..  there will be no restriction to build pressure behind the thermostat to force water the LONG way through the heater core and hoses..


..........

i would also like to know.. if you can verify that the heater and ac controls actually work the actuators..   when you move the levers around..    make sure that you can get it to defrost .. to blow toward the feet...  and out of the dash vents..

but the TEMP control is done by a different actuator..   and a different movable door.. ..


this is an infrared thermometer...  they are about 30 bucks in most parts stores .. some sell other versions for more...

allows you to point at a surface and see what temp is it..  this is an OEM brand from AZ.. Part Number: 25245

 

on a cold start.. you will want to verify that the upper heater hose stays cold.. until the thermostat opens.. then gets HOT..   then the fans come on...  the fans should cycle off in 20 to 30 seconds..

then in a minute or two..  then back on for another 20 to 30 seconds...

this verifies the thermostat is working properly...


you will also want to verify that the system on a cold start is NOT building pressure within the first minute..  that might show signs of a blown head gasket... not unknown on these motors..  the pressure will build slowly. over several minutes...