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skinny 01-05-2011 10:18 AM

Frost on the inside
 
Last night when I got out of work I noticed frost on the windshield. Got out the scrapper only to find out the frost was on the inside. It was almost the whole drivers side from bottom half way to the top. It was cold out, but it's been colder and never had this problem. I always make sure I turn the heat off before I turn off the engine. I did get it defrosted after a couple of minutes using the front defrost button and heat around 75. Any clue why this would happen now and not all the time?

robpp 01-05-2011 11:14 AM

Re: Frost on the inside
 
i would say you have a leak that has allowed water into the jeep. look for threads about the sunroof leaks. there is a TSB for the sunroof too.

Cherodude 01-05-2011 08:38 PM

Re: Frost on the inside
 
In cold weather it does not take a leak to get water inside the passenger compartment. Human breath, liquid water/snow tracked into the vehicle on your boots, a car wash, light snow drawn in through the inlets, etc. can easily put enough humidity into the air so that when the vehicle cools down overnight condensation can form on the inside of the windshield.
Just use the defroster and make sure you do NOT have recirculation 'on' (you want to get fresh outside air in to lower the interior humidity). Chances are this occurrence will be rare.

If a true leak exists, then of course you need to see the dealer pronto.

Also, I've never heard of this idea of turning off the heat before shutting down the engine. My cars have always had the heater left 'on' from about October to April for decades now, running or not. The difference in engine warmup is negligible in my experience, and certainly not detrimental, compared to human comfort. But then maybe this is just a Great White North thing? :)

mjw930 01-05-2011 10:40 PM

Re: Frost on the inside
 
Quote:

Originally Posted by Cherodude (Post 329093)
Also, I've never heard of this idea of turning off the heat before shutting down the engine. My cars have always had the heater left 'on' from about October to April for decades now, running or not. The difference in engine warmup is negligible in my experience, and certainly not detrimental, compared to human comfort. But then maybe this is just a Great White North thing? :)

Turning off the heat in the winter as well as the A/C in the summer is an old school idea from the days when the HVAC system was controlled by cables and pulleys. The idea was you needed to close all the vent flaps to seal off the inside from the outside. In modern climate controlled cars the electronics takes care of all the opening and closing the correct flaps, controlling the fan and delaying the "start up" of the system until there's enough heat (or cold) measured at the core before it starts pushing air. Turning it off does absolutely nothing beneficial.

For the last 15+ years most vehicles I've owned have automatic climate controls. I set it to 72 degrees, press Auto and never touch it for years.

skinny 01-05-2011 10:59 PM

Re: Frost on the inside
 
thanks for all the replies. I don't have a sunroof so nothing is leaking. didn't get it washed, no snow on the ground or precipitation. The weather has really been no different from before. Did not happen tonight and it was just as cold as the night before. As far as turning the heat off it's just a habit, but I can hear something shut when I turn the heat off. Figured it was the flaps closing. Oh well chalk it up to another thing that only happens sometimes.

rybocf 01-06-2011 10:04 PM

Re: Frost on the inside
 
As Cherodude mentioned this definitely can happen in certain conditions. It seems like the same concept as when the interiror "fogs" up when the relatively humidity is high inside and I assume the windshield is cold? I'm not an expert on this subject, but it obviously happens (same as when the OUTSIDE windshield fogs up when you run the AC and it's raining outside).

All it takes is the temp to drop to freezing when you have this condition and *poof*, fog turns to ice inside.

A leak would be a "trickle" line probably, and I'm guessing it would be top down and not bottom up (like air rising with changing temps)

Just a theory :)

-Ryan

skinny 01-06-2011 11:00 PM

Re: Frost on the inside
 
Quote:

Originally Posted by rybocf (Post 329744)
As Cherodude mentioned this definitely can happen in certain conditions. It seems like the same concept as when the interiror "fogs" up when the relatively humidity is high inside and I assume the windshield is cold? I'm not an expert on this subject, but it obviously happens (same as when the OUTSIDE windshield fogs up when you run the AC and it's raining outside).

All it takes is the temp to drop to freezing when you have this condition and *poof*, fog turns to ice inside.

A leak would be a "trickle" line probably, and I'm guessing it would be top down and not bottom up (like air rising with changing temps)

Just a theory :)


-Ryan

So far it hasn't happen again. Not to much humidity when it's only 20 degrees out, but anything is possible.

StoneCold 01-10-2011 01:32 PM

Re: Frost on the inside
 
Got to agree with what everyone else said. Moisture from your floor mats can cause it too, so take them out at night.

Put a bag of cat litter on your dash and that should stop it from freezing. You can buy specific 'room dehumidifiers', which are basically, fancy cat litter. I use them, cause, well, don't have a cat:o.


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