O.K., I am in desperate need of a good guess as to what the heck is wrong with my car. Klaus was the only previous respondent and he told me to go thru the glove box and check behind it to see if the main flap linkage for the windshield was broken.
Here is my problem: This morning it was 50 degrees F. outside temperature.
All windows are clear. As soon as I turn the heat on, regardless of whether it is set to defrost or just compartment heat, within 2 minutes I could not see out of any window. When I turn the setting to defost and close the front vents, there is no immediate clearing of the windshield at all. In fact the rest of my 25 mnute commute the windshield never clears. This has become a safety hazard as I am constantly wiping the inside of the glass with my hand to clear it.
I really can't afford to go to the dealer right now so any inputs that might make some sense would be most appreciated.
It also seems there is some residue on the glass when I wipe it off with my hand and this may be due to the fact that I think I need to replace the heater core. I have been losing a fair amount of coolant on a regular basis without knowing where it is disappearing to.

Thanks!

In your original post, it sounded like the defrost was not working:

"Does anyone know of any instructions/photos on repairing the main flap for the front windshield defroster? Having alot of trouble lately, all of a sudden trying to keep the windshield clear in the early morning."

Your current post is definately a leaky heater core.
www.matthewsvolvosite.com is a good site to look for replacing the core. I have seen one online site with pics on how to, but I can't remember where it is.

Klaus
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(V♂LV♂s 1975 164, 1995 854T, 1998 V70R)

You have the classic symptoms of a heater core leaking.

960, so you are saying that the heater core is the reason for the fogging?
How is that? When the core goes bad, does the internal tube leaking cause
coolant vapor to become airborne? Just trying to understand cause and effect,
like my 2 yr. old daughter.

Yes that is what is happening. The residue it leaves on the windshield after it evaporates is why you have to keep wiping it off. If you can't afford to fix it at this moment just disconnect the heater hoses at the firewall and connect them together with a piece of 1/2" tube and a couple of hose clamps. I limped mine through the remainder of the winter like that to avoid the repair during the cold weather. FWIW.

Yup, doncha smell antifreeze in the car?

Actually I don't and my wife says I have a pretty good sniffer.

My Dad's 850 had the same issue a little while back. The heater core, and evaporator, had to be replaced. Please let me recommend that you get this work done at the dealer, so that you can take advantage of the 1 year warranty on parts and labour that Volvo affords. Have a splendid Wednesday :)

p.s. You should also take a look at the cabin filter(if you have one installed) to make sure that it isn't clogged with debris.