Driving in a fog........

OKThumper

Registered User
The old girl (93 SC) just turned over 200k, and I have been fighting this problem since mile one. No matter what I try the car fogs up all the windows in cold weather. I did a search and found some references to "fog", "fogging", "defrost" and "defrosting", but nothing that is specific to this problem. When the weather turns cold enough to want to use the defroster the car just fogs up. There is no coolant leak as we have not had to add in for over two years, there is no sweet smell of anti freeze in the cockpit. We tried disconnecting the AC compressor, and it did not seem to make any differance with or without it. I checked the drain for the AC/Heater box and it is clear, I even flushed it out with a water/bleach mix to kill any possible mildew that might be holding moister. We replaced the climate control motor that operates the flapper. I am just at the end of ideas and need some guidance for someone that has had the problem and fixed it. Thanks for reading, shoot me some ideas........before I shoot the bird....uh tbird that is.

Thumper :) :confused: :)
 
you know windows do tend to fog up when there is a heat on one side and cold on the other, the thing to do is to hit the defrost switch but put it on COLD. thats what i used to do in mine, since i have no heater in mine.
 
Kind of like driving around all winter with the windows down........hmmm.........thanks but no thanks. Anybody else?????

Thumper
 
why dont u just buy, FOG X or go to ur local parts store and see if they have some ANTIFOG stuff for ur windows, or u can get shaving cream and rub it all over ur window and then clean it up, REPELS FOG nicely
 
You are supposed to open the windows slightly for a few seconds after you turn the control to defrost. However, your Outside/Recirculate solenoid or Outside/Recirculate Door Vacuum Motor may not be operating properly and not allowing outside air in. When you switch from A/C Max to Defrost, do you feel a flow of fresh outside air?
 
That may be a starting point, I am not sure that we are getting outside air during defrost. I will have to check for operation of the outside air door during defrost, I think it is working during the AC portion of the system. We did have to replace the blend door actuator at one time, but have not checked the fresh air door. Might take a day or two to get to it as I am swamped at present. Anything else to check while I am upside down and packed under the dash?

Thumper
 
These are all the things that I could think of. Some may seem far-fetched, but you may want to try them if the more obvious ones check out O.K.
1) Check if the cowl air inlet is blocked by leaves.
2) You can operate the Outside/Recirculate solenoid (which is near the blower motor and has three vacuum hoses) by applying 12v across its terminals. Check for vacuum at the outlet vacuum hose that runs to the Outside/Recirculate Door Vacuum Motor (I don't know why it's called a motor and not an actuator).
3) You should hear a momentary hiss when switching from one function to another. If there is no hiss or a continuous hiss, then you have a kink or leak in the vacuum hoses.
4) Is the heater working well? If not, the blend door may not be in the correct position for maximum heat.
5) Good luck.
 
Connect your AC compressor; its needed to defog your windows. Also, you outside air to come it. The A/C will lower the dew point of the incoming air, drying it out, it can then pass over the heater core to heat it up again. Its the dry air that pulls the moisture off the windows. Heat will by itself eventually dry out the air by baking it, but it isn't nearly as effective as the A/C. The S/C is setup to do this automatically whenever you run def or def/heat. Oh, it needs to be a working A/C with the capability to really cool the air. :)
 
Last edited:
Thanks guys. The AC works fine, I can almost make ice cubes in the summer. I had suspected that the air passed through the evaporator prior to the heater core, so that was a concern. I will have a chance to check out all of these by the weekend, and will report back my findings.

Thumper :) :) :)
 
Back
Top