help! windshield fogs horribly at the drop of a hat

[sinistral]

not sure what the problem is... but it is getting so bad my wife wants to get rid of the car before winter sets in (as she's driving it mostly these days).

as temps cool, or esp. during rain, the windshield fogs up crazily -- i'm talking condensation so bad you have to keep wiping it down to even try to see out the glass! the defroster doesn't seem to help, no matter the temp setting.

i thought, in fact, the defroster was causing the problem, as when the system is "off" there is still air coming up thru the ducts. as it starts to fog it starts in the pattern at the bottom of the glass above the ducts. looking at the stickies here, it sounds like the default "no vacuum" setting does in fact go to the defroster duct.

i'm not entirely convinced there isn't something wrong with the system (see my recent posts), but everything seems to work for the most part -- floor and defroster settings blow.

any suggestions? i do have a dash mat on there, but it's got cutouts for the defroster obviously and is velcroed down in place.

any insight appreciated. thank you in advance!

[L1011tristar17]

It could be a door in the plenum that is broken and doesn't shut/seal properly. Another issue could be a weak blower motor. That was the issue I had with mine, and swapping in a new blower motor (and fixing the frayed wiring) got rid of the issue for the most part.

[85crownHPP]

Is the inside (and outside) of the windshield good and squeaky clean? Sometimes it's as simple as that. Try some rainX anti-fog treatment too before getting rid of the car!

[IPreferDIY]

I might be somewhat off base, but I would suggest giving some thought to the heater core. I would think a heater core issue would be more obvious than what you describe, but I suppose there's a chance that just the right kind of leak could show up differently than what I experienced (i.e. a periodic white fog whose timing was presumably correlated with the thermostat opening up).

[sly]

+1 clean window
+infinity check the heater core for leaks (pull up the carpet at the firewall on the passenger side and see if it's wet with coolant.

[sly]

+1 clean window
+infinity check the heater core for leaks (pull up the carpet at the firewall on the passenger side and see if it's wet with coolant).

[87gtVIC]

I put money on the heater core leaking.

[miamibob]

I put money on the heater core leaking.

A likely suspect! Mine did just about the same till I bypassed it.

[miamibob]

I put money on the heater core leaking.

A likely suspect! Mine did just about the same till I bypassed it.

[nfldfordltd]

+1 on checking the heater core.
And stop dropping your hat.

[Brown_Muscle]

Does the A/C work? If it doesn't work, having the defrost on won't do jack, and will make matters worse if it's raining.

[sinistral]

Does the A/C work? If it doesn't work, having the defrost on won't do jack, and will make matters worse if it's raining.

interesting... AC does not work. so assume the AC dehumidifies the air? but wouldn't hot air be dry enough? plenty of cars on the road w/o AC.

i pulled the carpet on passenger side and didn't see anything noticeably damp. however, i do seem to have a leak *somewhere* since the coolant level drops over time. hmmmm.

in any event, i did just go out and buy some "rain X".

i'll have to dig deeper this weekend -- suspect i'll be tearing apart the dash after all (unless it really is the AC issue, in which case i'm out of luck -- estimates of over a $1200 to convert to the new system).

thanks, all.

[gadget73]

the AC dries the air, yes. Defrost works without it, but it works better if the AC works, especially when its warmer out and you don't want to bake yourself out of the car. Set to cold with no AC, it does squat. It also obviously does squat until the car warms up enough to make heat.

The heater cores seldom leak to the point where the carpet gets wet. It doesn't take much to steam the window though. If it got that sweet smell going on, thats a big clue that the core has given up.

[sinistral]

If it got that sweet smell going on, thats a big clue that the core has given up.

ah ha! sweet smell, yes...
but heat still seems to work?
core replaceable from junkyard, or chances are most are bad?
PITA to swap?
thanks!

[slack]

Heat could still work if the core is leaking but still flowing coolant through it.

I would go with a new core instead of a junk yard one.

Yes, as far as I know it's a PITA to swap. There's a few good write ups on this site though that should help you get an idea of what's involved.

Edit: Here's one: http://www.grandmarq.net/vb/showthre...-Core-Write-Up