Why does my windshield fogs up easily?
 

Hi,

I got my used '09 TCH last September 2010 and has been very happy with except for the annoying squeak in the right passenger seat (power seat). Anyway, here is the second annoyance I have been having lately, the front and rear windshield fogs up very easily. This only began happening this winter since the temperature is below freezing.

I live in Indy. Outside temperature is usually below freezing. The car is garaged (no snow accumulation on the hood and vents) and when I ran the car in the carwash, i always make sure aircon is in recirculation mode(as was recommended form this forum). I usually avoid switching to the front the defrost setting since this disables the ECO mode and makes the ICE run more that it should. But the fogging is just too stubborn.

The car is in prisitne condition and a Toyota Certified Used when I bought it. It doesn't show any sign of water damage. I was wondering if this is a normal case for the TCH. I never had this experience with my other cars.

Ed

Re: Why does my windshield fogs up easily?
 

Keep an eye on the level in the coolant bottle under the hood. When cold, the level should be right at the mark on the bottle marked 'cold.' When hot, it should be right at the hot mark.

If it remians low once the engine is warmed up, you may have a small leak in the heater core. This isn't very likely on a car this new.

If the coolant level remains where it should be, you may have a clogged drain tube on the A/C box. This prevents condensation from draining out, and when you turn on the defroster, the moisture becomes vaporized on the hot heater core.

Either way, your dealer should be able to easily diagnose the problem and fix it.

Joe

Re: Why does my windshield fogs up easily?
 

That's the problem. If you stay in recirculation mode you will fog up. When using the front defroster the system will turn off recirculating mode. If it doesn't the fogging would only get worse.

The main discussion that I have seen is where people do not like the default mode of the AC system starting in recirculating mode when you use Auto. It contributes to a stinking evaporator. That default mode can be changed by the dealer.

If you don't turn off recirculating mode when shutting the car down I can almost guarantee that you will have a stinking evaporator. It is much worse in more humid climates but could affect you in summer.

Re: Why does my windshield fogs up easily?
 

A myriad of discussions on this matter can be attain via Google search:

wwest nippondenso windshield c-best -dfg

Re: Why does my windshield fogs up easily?
 

I second the recirculation issue. You need to switch that off. By keeping the recirculate on in the winter, the moisture in the air inside the car gets to a level too high for the a/c to manage it. Also, windows will fog up easier if they are dirty/dusty, so clean them with a good product.

Re: Why does my windshield fogs up easily?
 

With the NipponDenso patented (US) two-layer cabin HVAC airflow design you cannot, in reality, fully switch recirculate off. The lower level, foot/floor level airflow is ALWAYS recirculated.

The best thing you can do is NEVER allow the system to go into cooling (dehumidifcation) mode during cool or cold climates, and ALWAYS use HEAT, LOTS of HEAT to defog the windshield and/or keep it form fogging over.

Automative A/C systems have very limited dehumdification capability in cooler and cold wintertime climates. Non-extistent dehumidifcation capability below ~35F OAT.

And keep mind that the A/C compressor will be COMPLETELY disabled by design with an OAT at or below freezing.

Re: Why does my windshield fogs up easily?
 

Correction:
The switching to recirculation mode I was referring to was ONLY WHEN I ENTER THE CARWASH. Which is often discussed in this forum, to put your A/C in recirculation when entering the carwash.Otherwise, I always put it off. ESPECIALLY when I set to defrosting.

Re: Why does my windshield fogs up easily?
 

every Japanese car i ever had had same fogging issue, bad or worse. old ones, new ones, does not matter.
i do not run a/c to dehumidify it, it costs gas.
i have $40 worth visor vents that work very well. crack pass side windows down maybe half inch, and all internal humidity is gone.
also, it's not as cold as it is in Indy, but still winter. i have my fan on window/floor and it starts right after i start the car. mo "sweating" issue at all.

Re: Why does my windshield fogs up easily?
 

Is it possible that you are confusing the air mix servo motor/door that allows mixture of hot and cold air with the fresh air door that controls outside or inside air from the blower?

Re: Why does my windshield fogs up easily?
 

I've uploaded the manual pages showing all the doors in the AC system.