Why does interior fog up?
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Joined: Jan 2006
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From: Suwanee Georgia
Why does interior fog up?
When it rains, and if I have the AC on or Heater on my windows start to fog up. It does not happen right away but it does happen. Today it rained and when I got to work no problem, get out of the car and go inside. 20 minutes later I looked at the car and the whole thing is fogged up? I dont get it. I thought I had a leak somewhere but the only thing I found was a very small drip comming from the rear hatch strut "taps". I sealed around the edges with clear silicone so that is fixed but WTF? Why the smokey windows when it rains?
Instructor
Joined: Jan 2006
Posts: 158
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From: MD
I have the same exact problem with my '90. My guess is the heater core has a pinhole leak and from what I remember about replacing heater cores, it's a major hassle. But I haven't pulled my Haines manual yet to see how much of the dash I have dismantle.
Instructor
Joined: Oct 2004
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From: Santa Rosa CA
There are several threads on replacing the heater core, the methods vary on how much of the dash you want to take apart for access. There is very limited room for working. I did it on my 89 by coming in from under the dash without removing any of the top or front. It is a pain but doable if you take your time. 
Le Mans Master
Joined: Jul 2002
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From: Alive and well in Burlington NC
Before you jump in a do the core, do a little investigation. If the vapor (steam) has an oily feel and you can smell anti freeze then chances are you do have a coolant leak and most likley at the core. If the steam really has no smell and evaporates relatively quickly, it could be just condensation build up in the ducts. If you have a little moisture in the duct work and blow warm air over it you will get a vapor (fog). This may be due to the changes in temp this time of year or perhaps a blocked cowl or A/C drain tube.
My $0.02
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Joined: Feb 2004
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From: Nashville Tennessee
When they build the Corvette, they start with the heater core and build the rest of the car around it. I will never attempt that project again. That is the one thing I would rather pay someone to do.
Safety Car
Joined: Aug 1999
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From: Fort Lauderdale FL
Originally Posted by mrmoore
Ifrom what I remember about replacing heater cores, it's a major hassle. But I haven't pulled my Haines manual yet to see how much of the dash I have dismantle.
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Joined: Jan 2006
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From: Suwanee Georgia
Good point, I do not smell antifreeze at all, and that smell is very distinctive. What it looks like is for example:
If you have ever rolled up your windows and turn on the fan (not the AC) when its raining there is nothing to de-humidify the air so humidity builds up around the glass.
I did think maybe the AC is not working as it should by removing the humidity from the air? It sucks though that my 86 does not have a button for "resurculate" setting for the AC. It only takes air from the outside.
The rain has stopped now for an hour and I am looking outside and the windshield and side glass have cleared up...go figure.
If you have ever rolled up your windows and turn on the fan (not the AC) when its raining there is nothing to de-humidify the air so humidity builds up around the glass.
I did think maybe the AC is not working as it should by removing the humidity from the air? It sucks though that my 86 does not have a button for "resurculate" setting for the AC. It only takes air from the outside.
The rain has stopped now for an hour and I am looking outside and the windshield and side glass have cleared up...go figure.
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From: Fort Knox, KY
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Hey, it might not even be a problem at all. Your car's HVAC panel has A/C and Defrost buttons which allow you to compensate for temperature variances inside and outside the vehicle that can make the windows fog up.
When you push the "defrost" button, it pulls in fresh air and turns on the A/C automatically.
Taking in fresh air, and de-humidifying it the windows de-frost faster, but keep in mind your A/C runs while this feature is activated so you might not want or even need to keep it on for long.
When you push the "defrost" button, it pulls in fresh air and turns on the A/C automatically.
Taking in fresh air, and de-humidifying it the windows de-frost faster, but keep in mind your A/C runs while this feature is activated so you might not want or even need to keep it on for long.
Last edited by onedef92; Mar 21, 2006 at 12:24 PM.
Race Director
Joined: Aug 2003
Posts: 13,421
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From: Lake Mary Florida
Well the air that enters the cabin whether hot or cold is passed over the AC evaporator it then enters the heater core housing and is either mixed with warm air or by-passed. A pin hole leak in the evaporator or a nearly clogged evaporator (it looks very similar to a heater core) may be causing your problem.
Prior to replacing my evaporator and after having replaced the heater core, I would pick up some minor fogging. It doesn't do that anymore with the new components.
Here is a picture of an evaporator showing a leak:
And one showing a brand new evaporator:
Prior to replacing my evaporator and after having replaced the heater core, I would pick up some minor fogging. It doesn't do that anymore with the new components.
Here is a picture of an evaporator showing a leak:
And one showing a brand new evaporator:
Safety Car
Joined: Mar 2005
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From: Winnipeg Manitoba, Canada
Originally Posted by PSO3120
When they build the Corvette, they start with the heater core and build the rest of the car around it. I will never attempt that project again. That is the one thing I would rather pay someone to do.
, im going to tackle mine in a few weeks!
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Joined: Aug 2003
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From: Lake Mary Florida
I have a PDF I created to R&R the heater core. PM me with email address if your interested. The file is 5.1MB.
I'm working on one for the evaporator but it's not even close yet to being finished.
I'm working on one for the evaporator but it's not even close yet to being finished.
Le Mans Master
Joined: Jan 2006
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From: Woodstock Georgia
Originally Posted by Steel Blue 91
Before you jump in a do the core, do a little investigation. If the vapor (steam) has an oily feel and you can smell anti freeze then chances are you do have a coolant leak and most likley at the core. If the steam really has no smell and evaporates relatively quickly, it could be just condensation build up in the ducts. If you have a little moisture in the duct work and blow warm air over it you will get a vapor (fog). This may be due to the changes in temp this time of year or perhaps a blocked cowl or A/C drain tube.
My $0.02
My $0.02
Race Director
Joined: Sep 2005
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From: Sharpsburg Georgia
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Originally Posted by PSO3120
When they build the Corvette, they start with the heater core and build the rest of the car around it. I will never attempt that project again. That is the one thing I would rather pay someone to do.
Been there, done that, more than once.
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From: Fort Knox, KY
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Originally Posted by blown87
They got that idea from a 2 series Volvo, and if you think that is bad try a MB s320, a evap core pays over 25 hours.
Been there, done that, more than once.
Been there, done that, more than once.
