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1997 SLS
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28 Posts
Discussion Starter #1
Can anyone help me with this? It's a hazard on cold nights, because my windshield fogs up. The heater blows out cold air when I select the "front Defrost" button, and set the thermostat to 70 degrees. The rear defroster works fine, of course, and it feels like the driver's side blows out moderately warm air, but the passenger side blows out ice-cold air and fogs up that portion of the windshield.

This is simply not optimal with the colder months approaching. I think this car has had this problem before when my father owned it (or maybe this is an on-going problem that was never fixed in the first place), but I can't remember for certain, and I can guarantee he wouldn't remember either, nor would he know what's wrong. So asking him isn't an option.

Bad heater core? Something electrical, perhaps? Any ideas would be greatly appreciated, thanks!
 

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-Administrator- 2002.5 F55 STS 2014 FWD Explorer
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66,258 Posts
When the windshield fogs, is the moisture on the inside or the outside ?

If it's wet inside, that's moisture from within the HVAC ducting, heater core, or the evaporator drain sump.

If it's wet outside, that's condensation of outside humidity onto the cold glass.
 

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1997 SLS
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28 Posts
Discussion Starter #6
Probably not.


Depends on what you consider "expensive", but I'd say yes. A dealer repair will be VERY expensive.
I have a reputable mechanic here in town that knows my car and specializes in Northstar and GM cars. I'm not dumb enough to take it to a dealership.

When the windshield fogs, is the moisture on the inside or the outside ?

If it's wet inside, that's moisture from within the HVAC ducting, heater core, or the evaporator drain sump.

If it's wet outside, that's condensation of outside humidity onto the cold glass.
Inside.
 

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-Administrator- 2002.5 F55 STS 2014 FWD Explorer
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66,258 Posts
First check the HVAC stack condensate drain fitting at the turn of the firewall to floor pan - just passenger side of center, probably hidden by a flap of soft insulation.

evaporator drain fitting.gif
 

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1997 SLS
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28 Posts
Discussion Starter #9
First check the HVAC stack condensate drain fitting at the turn of the firewall to floor pan - just passenger side of center, probably hidden by a flap of soft insulation.

View attachment 572663
I'll check that. I also pulled out the service records from February when it was in the shop:

On page two, under "Cooling System Complete Diagnosis", it says (among other things):

-Pressure test system, leaks found:
-Thermostat operation: leaking
-Cooling fan operation: ok
-Water Pump condition: leaking (this entire unit was replaced, as was all the belts and "HD Truck Thermostat/Engine Coolant Thermostat", as well as new coolant....see details below)
-Radiator Condition: ok
-All coolant hoses condition: ok
-Serpentine belts: ok
-Heater Core condition: ok
-Coolant protection level: low
-Performed engine block test: passed

Under "water pump - remove and replace", it says:

"As per recommendation, replaced water pump and all gaskets, replaced thermostat with belts and tensioner. Refilled and bled cooling, recheck no other leaks at this time."

Make of that what you will. This was all performed on February 5, 2019.
 

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Super Moderator
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86,074 Posts
Stay away from AutoZone "Don'tLast" parts, IF you end up needing a heater core.
Since it recently tested good, check that drain Sub mentioned first.
 

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1997 SLS
Joined
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28 Posts
Discussion Starter #11
Stay away from AutoZone "Don'tLast" parts, IF you end up needing a heater core.
Since it recently tested good, check that drain Sub mentioned first.
I have a membership to AutoZone, and their customer service has always been outstanding. I have no reason to stop using their services, however, I certainly won't use Duralast products.

As for the drain sub, I'll make a note of that for my mechanic. Thanks!
 

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1997 SLS
Joined
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28 Posts
Discussion Starter #13
autozone is good for ONE THING - free tool rentals
Tell you what....when they screw me out of a deal, part, or treat me like shit, then I'll shop somewhere else.

Besides, at least they aren't Baxter Auto Parts....you wanna talk about useless auto parts stores.....
 

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Super Moderator
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86,074 Posts
With moisture on the inside of the windshield (post #6), it sounds more like a heater core or a plugged A/C condensate drain.
 

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1997 SLS
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28 Posts
Discussion Starter #16
With moisture on the inside of the windshield (post #6), it sounds more like a heater core or a plugged A/C condensate drain.
To be fair, it's not that fogged....perhaps a little bit less than a quarter of the windshield on the passenger side. If I can, I'll take a picture of it and post it here.
 
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