Frozen interiors



My daughter drives a 2006 Ford F150. We live in the Midwest, not far from St. Louis (not exactly the frozen tundra of up north.) On New Year’s Day, she went to start her truck to go to work. She found the interior of the windshield covered with a layer of ice. The truck was not driven the day before. It was parked outside with the cab facing down the slope of the driveway. No windows were left open. The night before was cold, but clear and dry. She worried that as the ice melted when she scraped and defrosted the ice in the cab, the water would drip into the dash board, and possibly do some serious damage. Questions: How does the ice form on the interior of the windshield? What can be done to prevent this from happening again? What damage may have occurred during the freezing or defrosting process? Having listened to you for many years, I know you will have the answers (or some reasonable facsimile of such!)


If she was using the “recirculate” setting on the HVAC system, that would have allowed moisture from her breath to accumulate in the cabin. Later, when the temps dropped, that moisture would freeze.

Another possible cause is excess interior moisture from snow that was tracked into the car on her shoes.

Still another possible cause is a leaking heater core, but on a 2006 vehicle, this is not likely.


If this is a one time event I wouldn’t worry about it. Is it possible snow or water was tracked into the truck before it was parked? If it occurs on a regular basis, have the heater core checked.

To prevent this sort of thing, I’ve installed Vent Wind Deflectors on my last two trucks.

The wind deflectors let me leave the windows cracked when the truck’s part. This prevents any moisture buildup. Plus, it keeps the truck cooler in the summer.

Ed B.


This is not an unusual occurence. When a person breathes, some moisture is expelled. This moisture will condense on the coldest surface, which is quite often the windshield. When the termperature dropped below 32 F., the moisture froze.
I have had this happen on my cars. I have short handled rubber squeegee that I carry to remove the ice from the inside of the windshield. The cab of your daughter’s F150 is probably tight as it should be. This helps promote the ice formation on the inside of the windshield. It doesn’t do any damage.
My dog has suggested to me that I drive with my head out the window as he does to prevent excess moisture from developing in the cab. However, I would sooner just scrape the ice off the windshield.


Thanks! Any risk of damage with the water going into the dashboard?