When it started to cool down this year I noticed my car was not putting out heat. This will be the second winter I had this 2002 S-type. Last year the heat was fine. I’ve been all over YouTube and Google and I can’t find what I might be missing. The first thing I thought was the problem was that the heater core was plugged. I back flushed my heater core with compressed air and flush it with a garden hose through a flush kit I installed. I also flushed my radiator while I was at it. This did not fix my heat problem. Next I thought it was my heater control valve. I remove the # 1 10amp fuse in the engine compartment. Didn’t give me heat. I unplugged both hoses going to the heater core and turned my car on with the heat on high. There was no coolant coming out of those hoses. Assumed the heater control valve was bad. I did unplug the power from the control valve and test it with a multimeter. I was getting about 14volts in the center prong. I bought another heater control valve and installed it. I refilled my coolant and bled the air out with both bleeder valves. Still no heat. The lines going to the heater core was hot and when I cracked the cap to the flush kit “T” I installed on the output side of the heater control valve hot coolant came out. The return line coming from the heater core was very hot could not touch it with my bare hands for more than a second. Still no heat. My car is blowing perfectly cold air as if the engine was not warmed up at all. Thermostat seems to work fine. What could I be missing? Any help would be greatly appreciated.

 

By the way I have the 2002 V6 S-type.

 

Heater pump.

Please try to use line breaks for easier reading.

 

The S-Type 3.0 V6 does not have an auxiliary heat pump, that is installed on the V8 engined cars.

Do a search of this forum for CCM and DCCV as both can cause the loss of heat you describe.

 

Last night when I got everything hooked up I let the car run for about 20 mins while I was checking everything. My engine temp was at the normal level. There was nothing but complete cold air blowing from the vents. This morning when I went to work my heat started working just fine. The heat is really hot on high and when I set it to temp the heat cools and heats up just like it supposed to. Thanks for the help.

 

Excellent! Air-lock was the likely culprit, and worked its way out after the system cooled.