I have a 2002 Ranger XLT 4x4 A/C 4.0l. I have had the truck since new. On many occassions when I start up the ventilation system, it blows a short blast of moisture onto the window. This causes it to fog up for a few seconds (maybe up to 10) before it blows off. It doesn't seem to matter if it is sunny out or raining. Although functionally this is no big deal, it is still a nuisance. The dealer says this is normal and will not fix. They claim that many late model Explorers, Rangers, etc. have the same behaviour.

Any body else have this type of problem?

Any ideas on what can be done to remedy this?

Cheers!

 

Same happens occasionally with my 2001 explorer, so the dealer is right -you are not alone. I don't have any coolant leaks so that's not the cause. It is not a a big deal if sitting in the driveway, but can be problem if it happens when driving since it does take a few seconds to clear.

 

Normally if that happens it is a leak in the heater core. Maybe just a loose hose or fluid where it should not be.

 

This used to be a very common problem, years ago. You would run the A/C on a warmer day, then shut off the car or truck. The next morning when it was cool out, you would start it up, and humid air would flow out of the defroster ducts right onto the cold windshield, fogging it. I believe the real problem was the climate control system not being vacuum tight enough to hold it in the last set position, like dash vents.

When you shut off the vehicle the day before, condensation water was left on the A/C evaporator core. When you start it up again, the airflow will blow that very humid air out for a few seconds till its gone. If the climate control vacuum had held the dash vent position, it would blow it out at you, you would go "whew!", and that would be that. But if the vacuum slowly disappears when off, then the vac motors that position the air flow will go to their default non-energized positions, which is DEFROST (at the windshield) for safety reasons. So the humid air hits the windshield, not what you wanted.

The way I solved this in the 70's was to switch to VENT a few minutes before shutting down for the day if the A/C was on, and running the fan up to a higher speed. This purged the system of any remaining moisture on the A/C evaporator. So the next morning, there wasn't any humid air to get blown onto the cool windshield.

Thats what I figured out, anyway.

 

Like Torky said, its just trapped humid air in the system. If you had a coolant leak you would smell it, and the fog on windows will not go away.