Windshield Fogging Up.
Thread Starter
8th Gear
Joined: Mar 2023
Posts: 8
Likes: 0
Windshield Fogging Up.
Hello, with the temperatures starting to drop where I live I have a few questions. I got my 1985 earlier this year and I have been daily driving it. I have not driven it in cold weather yet. Today was the first cold day I drove it. Within a few minutes every window in the car had completely fogged up. I had to wipe off a patch on the windshield to see. My question is: Is this normal? Is there a defogger or a way I should have the climate control set? A few other things I noticed earlier is that sometimes I get a fog patch in the center windshield what seems to be a kind of film it usually goes away eventually, I tried to wipe it off yesterday and that didn't do much. I also sometimes get a very small amount of a white mist when I have the AC blasting. Any help would be appreciated thank you.
Intermediate
Joined: Mar 2016
Posts: 43
Likes: 5
You likely have a leak somewhere. Check the seals around all the windows, windshield, rear hatch, etc. Mine leaks ever so slightly but the defrost does a good job to keep the fogging to a minimum.
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Le Mans Master
Joined: Jul 2004
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From: Clifton Park, NY ............Clearwater, FL ... 85 Original Owner
Le Mans Master
Joined: Jul 2004
Posts: 6,227
Likes: 697
From: Clifton Park, NY ............Clearwater, FL ... 85 Original Owner
Drifting
Joined: Jun 2013
Posts: 1,963
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From: Shell Point (Crawfordville) Florida
The fog on the windows is moisture in the car from your breath condensing on the cold glass. If the defroster is on then the AC should be on (automatically) so that it can dehumidify the car and the windshield. If the AC is on even in the vent or heat mode it will dehumidify the car and clean up the fogged windows.
Pro
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From: Northern California
2nd Gear
Joined: Jan 2026
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Le Mans Master
Joined: Jul 2004
Posts: 6,227
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From: Clifton Park, NY ............Clearwater, FL ... 85 Original Owner
Drifting
Joined: Jun 2013
Posts: 1,963
Likes: 342
From: Shell Point (Crawfordville) Florida
You can turn on the AC and put the temp on warm or hot or whatever you want. AC does not mean only cold. If you have the electronic control put it on AUTO and set the temp, if you have the manual control turn on the AC and set the temp. With the AC on your windows will clear up in a few seconds. You do not have a leak.
Melting Slicks
Joined: Nov 2016
Posts: 2,253
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From: So Cal
2023 C4 of the Year Finalist - Unmodified
This is a 1985. The 85 has a heater core control valve and manual controls. When the temp lever is moved off of full 'cold' the valve is opened and coolant flows through the heater core. (When full cold, the 85's valve bypasses the core. No core flow in 'cold")
When the valve is open, the Sophiae's windshield fogs. When it is closed, it does not.
It seems to me that the Sophiae's heater core is leaking.
When the valve is open, the Sophiae's windshield fogs. When it is closed, it does not.
It seems to me that the Sophiae's heater core is leaking.
Drifting
Joined: Jun 2013
Posts: 1,963
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From: Shell Point (Crawfordville) Florida
After a ride with the AC on, either cold or warm setting, when you stop and park the car, the water dripping out underneath the front of the car is the moisture that had been removed from the cabin if you had it on recirculate. If set on outside air that dripping is moisture removed from the outside air that enters the cabin.
Either way the AC removes moisture from the air.
Either way the AC removes moisture from the air.
Race Director
Joined: Dec 2002
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From: SCMR Rat Pack'r Charter Member..Great Bend KS
There is a drain for the AC condenser. Sometimes this gets clogged with dirt/leaves/seeds/etc. and the condenser housing fills with water. When this happens, nothing you can do will prevent fogging.
You have to find the drain line and clear it.
You have to find the drain line and clear it.
Drifting
Joined: Jun 2013
Posts: 1,963
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From: Shell Point (Crawfordville) Florida
IHBD - if the heater core was leaking, wouldn't there be some evidence of that, like water on the rug on the floor inside the cabin as well as the odor of antifreeze inside the car, and maybe slowly dropping levels of coolant in the tank? The moisture from coolant on the windshield is usually slimy/sticky, not just water condensing on the cold glass.
Rocco's suggestion sounds more likely to me, especially if the car has been outside most of the time as opposed to being inside a garage where that crap would not constantly fall on the car and get past the screen by the windshield. Chestermo said this in post #2.
Rocco's suggestion sounds more likely to me, especially if the car has been outside most of the time as opposed to being inside a garage where that crap would not constantly fall on the car and get past the screen by the windshield. Chestermo said this in post #2.
