Moisture Inside My Car Overnite

[Tncobra]

If it had a heater core leaking it would be antifreeze leaking and would not freeze on the inside of the windows.

A leak inside causes the windows to condensate.

[Guest Jamie]

Hopefully...LOL...but in the last 10 cars i've owned...when the car is "fogged up"...I hit that "A/C" button and boom...fog gone.

That's because you changed the temperature of the air inside the car and caused the moisture to return to vapor instead of liquid form.

When the air inside the car is warmer than the outside temp, the water condenses on the windows and any other surface... same as it does on your nice cold beer inside a warm room. But if you lower the temp to what it is outside... or drop it even lower... then the water evaporates off, back into vapor/gas form. It doesn't really leave the area, it just quits being a pain in the ass.

Crank the a/c up high enough, and get the inside cold enough, and the fog will form on the outside of the windows, when the weather is damp.

[Guest MERRILL]

Guys, the A/C doesn't do anything but lower the air temperature... it's not a de-humidifier. And moisture removal is accomplished by where the air is sent, and what it's sent through... or raising the air temperature and "burning" the humidity off. ( It still has to be pumped to somewhere else though. )

Wrong. If you lower the temperature of the air, moisture will condense. Air conditioners are dehumidifiers. Where do you think that water comes from when your air conditioner is on? It comes from the air. Raising the air temperature does not burn water off. It just increases the capacity of the air to hold moisture.

[Guest Jamie]

Wrong. If you lower the temperature of the air, moisture will condense. Air conditioners are dehumidifiers. Where do you think that water comes from when your air conditioner is on? It comes from the air. Raising the air temperature does not burn water off. It just increases the capacity of the air to hold moisture.

It's the temperature of the GLASS that causes the moisture to be "sucked" ( condense ) out of the warmer air in the car.

( the outside air is colder than what's in the car, but drops the temp of the window glass. )

Again, think about a glass or can full of iced whatever in a warm room... it sweats and drips. Put it in a room the same temperature as the contents... no more dripping.

Simply changing the temperature of the air inside the car... or even the car/glass it's self... won't remove the moisture though. It has to be sent somewhere else.

In this case, I suspect the OP's problem is figuring out where the water is coming from to begin with.

By the way... how do you figure a blow dryer works? It heats the air up, causing the water to evaporate, then relocates said air ( along with the water that air is carrying ) someplace other than your hair.

Edited December 22, 2010 by Jamie

[Tncobra]

Simply changing the temperature of the air inside the car... or even the car/glass it's self... won't remove the moisture though. It has to be sent somewhere else.

The moist air is brought back through the evaporator core escaping to the ground from the drain in the box.

May have been said before. Newer cars a/c compressors cycle when in defrost mode to accomplish removing damp air.

Now we all need to inspect this car to end the thread!

[Guest Jamie]

Newer cars a/c compressors cycle when in defrost mode to accomplish removing damp air.

A 2009 Chevy HHR don't. It just doesn't give you the option of recirculating the air. It auto-selects fresh air and that's what you're stuck with.

I know this for a fact, and it pisses me off, because I don't want the car deciding ANYTHING for me.

And yes, we need to inspect the OPs car...

[Guest buttonhook]

( I'm assuming the laws of thermodynamics, condensation, and evaporation haven't been changed in the last, oh, 30 years or so? If they have, I didn't get the memo.)

you didn't get that memo?........the laws of physics no longer apply. they are just guidelines now

[Guest Jamie]

you didn't get that memo?........the laws of physics no longer apply. they are just guidelines now

Well that would explain a lot. :-\

[peejman]

While the A/C compressor may run when the defrost is used in the car, it's only when the outside temp is above the point at which frost would be forming on the glass. The compressor typically does not run when the ambient temp is below about 40 deg. It can't build adequate pressure at low temps. Try turning your home A/C on when it's below freezing. There's a temp sensor that'll prevent the compressor from running.

Another thought... it's possible that after running the engine for a few minutes, the underhood temp may increase enough to allow the compressor to cycle.

[Guest buttonhook]

just like the constitution......

[Guest Jamie]

I'm starting to think there's only one real working solution to the OP's problem:

A wheelbarrow-load of silica gel packs in the backseat of the car. It's the one sure way to suck up all the humidity and keep things from fogging/frosting up.

[Guest db99wj]

I'm starting to think there's only one real working solution to the OP's problem:

A wheelbarrow-load of silica gel packs in the backseat of the car. It's the one sure way to suck up all the humidity and keep things from fogging/frosting up.

Just don't eat the silica packs.....it says so, right on the pack.

Do you lock the doors at night? Someone might be sleeping in it.

It would check the moon roof seals. With my Jeep I have to be careful with the seals so that it doesn't leak. Course, mine actually comes with drain holes in the tub from the factory!

[Guest Jamie]

Do you lock the doors at night? Someone might be sleeping in it.

... or something.

[titan14]

Well...obviously i dont know what the hell I'm talking about...and haven't experienced it first hand in ALL vehicles I've owned with an "A/C" button...so...with that being said...sorry OP ....I have no freaking clue whats going on with your car. Good luck...and hope you get it fixed.

[ftncityfatboy]

Well...obviously i dont know what the hell I'm talking about...and haven't experienced it first hand in ALL vehicles I've owned with an "A/C" button...so...with that being said...sorry OP ....I have no freaking clue whats going on with your car. Good luck...and hope you get it fixed.

[Guest Lester Weevils]

If there are no leaks, something as simple as an extension cord and a 40 watt incandescent bulb in a worklight, left on in the auto at night, might chase out the humidity. Assuming the auto is close enough to the house to make it practical.

Would be better to verify no leaks in seals or the heating system of course.

Warm air has low relative humidity. When warm moist air cools off, the relative humidity rises and when it gets too high you get the condensation.

Pianos are humidity sensitive. Too little humidity is bad for the sound board, and too much humidity causes the piano to stretch sharp. If humidity continually rises and falls it pulls the piano out of tune too quick, and of course if the piano is just too sharp on humid days its no fun playing along with other instruments that must tune against the piano. So in simple cases you can put damp-chasers in the piano, long tubes with very low-watt heaters which are barely warm to the touch. In rarer more complex situations, pianos also need humidifiers, with a humidistat controlling whether to run the damp chaser or the humidifier.

Amateur astronomers who have the little fiberglass domes in the back yard, often have condensation troubles, and those issues are often cured with as little as a 40 watt light bulb (or lower power) left on in the dome. Apparently it doesn't take a lot of heat to chase damp in many cases. Amateur astro-domes are not huge, but have more volume than a typical car. A low-watt bulb might work for the car too.