Won't defrost

Hi all. I have a 98 150, and suddenly my windshield won't defrost. I have heat, my fan works and there is heat coming out of my defroster vents, but my window never really clears. I checked my A/C and it seems to not blow all that cold. (cool, but not as icy as usual.) Living in Michigan, this could be a problem. Any suggestions as to what I (or my husband) should check? What can I do in the meantime? (I have a bad belt and a ball joint that should probably get fixed first.) Thanks.

Is the windshield grimey? with a film on it? If so look for heater core leak.
Another remote possibility is the recirc door is stuck in recirc position- seen this one or twice- the interior will fog considerably in humid conditions around40 to 50 degrees if the recirc door is stuck in recirc position...

My defroster on my Escort barely puts out any heat at all. Have asked around and everyone says they have a poor defrost. Barely any air comes out even though it is fairly warm. I think it is something you will have to live with unless the heater core has a leak in it. If so it would be dripping onto
the carpet. No drips--good heater core.

Sounds to me like there is an issue with vacuum getting to your control head in the dash. Alot of times you can find your vacuum source, follow the line and see if you have any type of vacuum leak from your supply all the way to your control head. if you are getting vacuum supply all the way to your control head give me a reply and i will dig some more for you. let me know if this helps

If you have heat coming out of your defrost vents and you can feel the air flow getting to the windshield everything in the dash is working properly. One thing that people do not understand is that in order for "defrost" to work you must have proper a/c operation also. What I would recommend doing is going and getting your a/c system checked out and fixed. Once your a/c is fixed your defrost should start working again. PLEASE PLEASE find a reputable shop,...if you want to let me know where you are located and I can find you a reputable automotive shop.

I failed to mention that when there is something wrong with the heater as far as the blend door or worse the system goes to defrost by default. This insures that you will have a clear windshield if the whole system goes down.