Car instantly freezes

Strangest thing… I turn the heat on in my car… It was a bit cold still, but all of a sudden all of the windows glaze over in a frost… rear view mirror and even the gauge cluster and the cheap vinyl dashboard… I couldnt see anything!!! Slowly, the defroster cleared up the front window for me to see…

what would cause such an instantaneous freeze? Besides being cold outside… 0 was the temp…

M

Moisture in your ventilation system, I’d say, possibly a waterlooged filter or something.

So there was moisture in there… heat comes on… spreads said moisture all over the car windows, dash… hmm makes sense…

If you have air conditioning the drain may be plugged and thus water has accumulated in the vent system. Talk to a mechanic who is familiar with your model car about how to clear it.

By the way, if you have A/C you can use it in combination with the heater to quickly clear fog from the inside of the windows. When the incoming air goes through the A/C it gets dried out (water condenses on the A/C and goes out the drain) and then after the it passes over the heater it becomes hot, dry air and thus clears the windows much faster than outside air that was merely heated. Some cars have a defrost button that runs the A/C plus heat, turns the fan up all the way and directs all the air to the windows.

You either got some snow, ice or water in the vent system or you have a pin-hole your heater core.

The heater core problem will continue to occur until you get it fixed.

The water or snow in the vents should be a rare event.

Did you smell antifreeze while this happened? Were the windows kind of oily afterwards?

Well one, the A/C system does not work… Compressor never turns on…(summer Project)… it was snowing today too. I didnt smell any anti-freeze or feel any oily substance… I guess the question is will it do it again?? Ill know later today :o)

There’s a good chance the drains for air intake under the windshield cowling are restricted. While these can sometimes get clogged with “tree debris” (leaves, etc.), if this is the first time you’ve had this symptom it’s more likely that packed snow and/or ice is the culprit. If the problem goes away by itself, particularly after the car has been warm enough to thaw, that’s what I’d suspect.

It could also just be dew point. You have a miniature climate region inside your car that you can control. When you get into a cold car and turn on the heat, you are basically causing a warm air mass to collide with a cold air mass. If the humidity conditions are right, and the dew point is right, you are going to get instant condensation on all surfaces. Sort of like when moisture forms on the outside of a glass full of iced liquid.

I think Chefguy’s on the ball. My car works perfectly fine and nothing’s clogged, and on really cold mornings my interior side windshield will fog and freeze as soon as I turn on the defroster. The A/C compressor does come on automatically, but the fan is already blowing before the compressor actually kicks in full strength. So the fog’s already frozen by time the dehumidifying characteristics take over. The end result is, you’ve got to wait for the air to get warm and melt the frost before any humidity is removed from the windshield.

So where’s the initial moisture come from? It’s already in the car, but pretty much at equilibrium. As soon as you turn on the fan, you’re compressing the air that’s blowing. As soon as the blown-out air re-expands, the water in that air suddenly recondenses.

Well, it did it again on the way home… as soon as it kicked on… BAM everything is frozen! heh… Did smell a faint coolant, nothing strong though or oily…

Once the heat gets up to par everything clears up, so its probably just not having the A/C working (thus takes longer to clear up) and being so damn cold outside… Never really drove this car in 0 and below weather…

Thanks for the info everyone…Informative!

M

I’m pretty sure compression by the fan has nothing to do with it. Since your car likes to run the AC without your consent, I’d bet that the AC core is well covered with condensate when you shut the car down. The moisture just hangs around and supersaturates the air in the ventilation system until you start the car up again in the morning. As soon as the blower kicks off, the supersaturated air comes out and condenses moisture on everything. I’ve often noticed this “feature” on cars that like to run the AC automatically.

This is also a contributing factor to “stinky AC” problems.

If you’re smelling coolant at all, this is probably the source of your excess moisture. Although it’s not common, sometimes leaking heater cores can rupture suddenly, dumping lots of boiling hot coolant onto your ankles. Not good.

Heres whats happening;

You have a small coolant leak in the heater core. When the car warms up the
metal is either expanding and closing the hole, or the warm air blowing on the windows is enough to keep them clear - until you let the car cool down again and have to start the process all over again.
IOW;
The small leak allows a little moisture to accumulate in the vent right around the heater core.
You start the car and the blowing air is cool and moist - hence the fogged up windows.
As the car warms up, the air also gets warm enough to clear the windows, and/or close the leak.

Until you figure out for sure what the problem is, I recommend adding
Bar`s stop leak until you can get it fixed. Also, run the car untill it gets good and warm before you start the blower, that will keep the windows clear until you stop the leak.