Foggy windshield on 2001 lincoln

Open the hood, on the passengers side lower windshield plastic cover there's a flap that's supposed to let water drain through, these constantly get clogged with leaves and crud allowing water to back up into the fresh air intake for heat and a/c..clean the drain and run hose water down windshield and make sure it'll drain properly. People have been known to remove the rubber flap to allow better flow.you'll want to check this regularly for build up of debris, especially if you park under or near a tree, bush..

Is it fogging up when you use the heat or a/c? Is it fogging up after sitting outside on a particularly dewey night?

An easy fix and one to try first is turning the temperature gauge over toward heat, and setting the directional controls to defrost. Up the power on the blower for a moment. The warmer air will usually clear up a foggy windshield in seconds on a chilly or even not-so-chilly morning. The condensation on the glass needs a change of temp in order to evaporate. Sometimes you can get the same effect by using outside air to circulate through your car's blower system. Most have a way of circulating either inside-car air, or outside-car air.

If the glass fogs when you're driving down the road and have the heat on, or the a/c - do you smell something sweet or see white smoke coming out of your air vents? If so, you could have a faulty heater core. I wouldn't imagine this is the problem on such a new vehicle, but it could still malfunction.

Of course, if you're trying to wipe this fog clean and it won't go away, maybe you've got someone smoking in the car and leaving a film on the glass. It would take a lot of smoking to make the windshield look foggy though.
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Are you sure that the front floor is not also? look under the floor mat, is the water clean or does it feel slick. If slick then you most likely have a bad heater core. Do you have to add engine coolant often? If you run your defroster does you windshield fog up? Another sign. Does this only happen after you go through a car wash or a rain storm?

if the fog is on the inside of windshield and does not feel oily i would look for a water leak into the heater asm or the vehicle. if moisture on windshield is oily,then the heater core maybe the cause due to a leak.
good luck! check UNDER the carpets for water!!

If it gets wet wen not driving in the rain and if your windshield is not fogging your air box drain is clogged if you are losing coolant and the windshield has fog your heater core has a leak

Sounds like you need a new ECU unit ,dealer only

It may be set to recirculate the inside air, this is indicated by a symbol of a car with a swirling arrow inside, the button will be in with the climate controls. always use outside air if it is cold or raining and you will avoid fog

Hi ....... Sounds alot like you have a grounding problem on your HT leads (central one from coil esp'ly). At night when it's dark open the bonnet/hood and start the engine. Look for any sparking or arching from plug leads, coil or ignition box. Stop engine. Find where your leads come from, four will come from a central point and make sure all conections are tight. Even remove and look for corrosion, only take off one at a time to avoid confusion and when you're happy that they're OK buy some WD40 and spray near coil and over leads and allow to dry off. This will help to prevent moisture to penetrate and will cure the problem short term.
Let us know the outcome.