jim999

Hi,

This is a general question i think (not specific to camry's - but maybe not). It seems that whenever it rains, the windows in my car fog up.
Now it seems to be worse in the fall and spring, where it is cool outside, but it still happens in the summer. The problem multiplies of course when there are more people in the car.

With my defrost do i use cool air or warm air? what about the swithch which controls whether the air is re-circulated or brought in from the outside.

This problem is quite annoying, and one of the solutions is to open the window, which makes the people behind me very unhappy.

Any suggestions would be appreciated.

Thanks,

Jim

James Bond 007

There are few things that could cause this Moisture in the car, damp towls or what ever else thats damp, a leaking windshield or leaking sun roof and finally a leaking condenser (Looks like a small radiator usually on the pasenger side, behind the dash board)and is part of your heater.Try touching the carpeting on the pasenger side or leaving news paper down for the day and see if it's damp or try this, leave your windows down an Inch and a half for the night, very little fog will be there by morning.You can use hot or cold air to defog your windows.The fog is most likely caused by the temperatur diffrences inside and out side by keeping the windows slightly down you are now, some what, equilizeing the temperature

a.p.landes

Jim999, The solution is quite simple. Unlike alot of US cars you have had, these vehicles need the AC turned on under these conditions. Yes, leave the heat to normal thermostate, and simply hit the AC button and you will see what I mean. When fogging does not appear to be a problem then turn AC off. This has been a fact for years. Most US cars have automatically kicked in the AC without you knowing it. Your manual will tell you this if you have one. I found this out 20 years ago on an old Honda. Let me know how it works. Paul

wwest

Given that your vehicle is of Asian/Japanese origin the climate control system is most likely of NipponDenso, Denso USA, design. With the change-over to the new less efficient non-freon refrigerant several design changes were deemed necessary.

First, the A/C cooling evaporator, heat exchanger, was made a lot more dense and complex. The more chilled surface area for the air to flow over, the higher will be the efficiency of the heat transfer.

The second issue is more directly pertinent to your problem. The slower the air flows over the evaporator's cooling surfaces the more it will be cooled and the more it is cooled raises the likihood that it will be simultaneously DEHUMIDIFIED.

Another benefit of the lowering of the incoming airflow rate is better MPG, something I'm sure the automotive manufaturers haven't over-looked. Almost all modern day passenger vehicles are very well sealed against atmospheric outflow for these reasons.

The way NipponDenso has chosed to keep the evaporator airflow as low as possible is by restricting the cabin atmosphere OUTFLOW. The result of that is that during the cooler months it will be really easy for the passenger cabin to become extremely humid, so humid that the windows and windshield interior surfaces, cooled continously by exposure to COLD outside atmosphere, begin to fog over.

My suggestions...

If it is possible to completely disable the A/C during the winter months then do so. My 01 RX300 has C-best options which allowed the dealer to "unlink" the automatic operation of the A/C in both "normal" and defrost/defog/demist modes. ON a previous 92 LS400 I fooled the system into thinking the OAT was below 32F by adding a resistor in series with the OAT sensor. I have also, on occassion, simply disconnected the A/C compressor clutch electrical circuit. My 01 Porsche has a switch added within the glove box that does that.

If you park the vehicle inside it will help to leave a window or windows open so the cabin can more completely dry out. During A/C operation the ~10,000 square inches (92 LS) of evaporator surface area will become saturated, clogged, with mositure and while much of that will drain away via the provided drain a lot will remain and then evaporate into the A/C plenum and thus into the passenger cabin at the first start of the system blower.

My most common occurance of intermittent and spontaneous windshield fogging was about 5 miles into my morning trip to the office during the cooler months. That instance was cured, mostly, by leaving the windows slightly open during the night in the garage.

Another instance is that the A/C compressor will oftentimes shut down spontaneously, without any indication to you, if the OAT declines to near or below freezing. A few minutes after that happens the condensed moisture remaining on the evaporator will begin to evaporate into the airflow entering the passenger cabin.

Be VERY CAREFULL, this can be a very HAZARDOUS situation.

If you are traveling in a colder climate and begin to see wisps of condensation on the interior surface of the windshield DO NOT ACTIVATE the defrost/demist/defog function before you turn the system heat all the way to MAX!

Those wisps of condensation might be indicative of the A/C compressor having previously shut down due to low OAT and now if you activate the defrost/defog/demist function the COLD windshield will become suddenly opaque from condensation due to the moisture bomb building up with the A/C plenum.

The best procedure to use if you sense that the humidity is to high within the passenger cabin is to lower the rear windows slightly and quickly purge the humid atmosphere from the cabin.

While I remain a strong advocate of the use of A/C to dehumdify the incoming cabin airflow and thereby help to remove windshield condensation and prevent it's formation, I don't understand why, other than the slight discomfort one might feel, the defrost/defog/demist airflow isn't also HEATED.

Wwith Outside Air Temperatures, OAT's, below about 55F it is impossible to predict whether or not the the A/C can be efficient enough to be of any help. The A/C's dehumidifcation efficiency is a function of the relative humdity of the incoming airflow. The lower the temperature of the incoming airflow the lower is the probability of efficient dehumdification by the A/C until at about 35F it is practically non-existent.

sourcerer

I have found that avoiding use of the air recirculation switch on the heater has helped keep fogging down during the winter months.

I suspect this is because the outside air is relatively dry in the winter. But if you use recirculated air and the heater together, you wind up vaporizing the moisture that enters the car through the snow on your shoes, etc. That moisture stays in the car because the same air is being recirculated, and then of course it condenses when it hits the cold windows.

Switching over to fresh air intake made a big difference most days.

fredbros72

hey , usually the recirculation mode will cause the fogging, just leave on fresh when you can, should solve the problem mostly