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Lincoln heater problem

My wife’s 2002 Lincoln LS has an HVAC problem. When it is cool or cold outside and the thermostat on the console is set for 78 or 80 degrees or so, the system puts out COLD air.
When the temperature outside is warm or hot and the thermostat on the console is set to cool the interior, say 70 or 72 degrees, the system puts out WARM air.
The dealer can’t seem to duplicate it. Their solution several months ago was to replace the air conditioner compressor. It changed nothing. I think we make a boat payment for the mechanic.
It would seem to be a sensor is defective and reporting the wrong temperature.
What’s wrong with it?

Where do you want to start?

It could be the vent control module which controls every component in the vent system. Or it could be the auxiliary coolant pump or its relay.



Is the system capable of producing hot air out of the defroster vents, when you set the temp knob to high?

OK, she finally let me drive it…
It doesn’t have a temp knob, but a digital setting, for left and right side.
I can get cold air out of the vents, when set on “60” degrees; …and when the control is set to 90 degrees, warm air comes out of the vents.

OOPS, you asked for DEFROSTER vents. Went back out and tried it. On defrost setting, at 85 degrees, no flow, heater motor kinda quiet; on 90 degrees, motor speeds up but there is only a little flow from the center of the vents under the windshield, very little of none at the sides.

OK, the suggestions are to check the Vent Control Module, the Auxiliary Coolant Pump, and the Auxiliary Coolant Pump Relay.
Any other suggestions?


I say you have a blend door motor not driving. You are getting outside. There is a motor for the defrost door too.