Steamed up windows, bad heater core???

This old girl is steaming up the windows what should I do? :evillol:

Seriously, a friend of mine has the 1990 Aerostar and when she turns on the defrosters it steams up the windshield.
Is this a common problem with Aerostar? Heater core? Does the Aerostar have a flow control valve in the coolant line?

Just need to know what I am getting in to if I offer to fix it.:uhoh:
Thanks for any advice.

Sounds like the heater core is leaking. Replacing the heater core can be an adventure. Read a repair manual and look at what is involved and to become familiar with the job. Breathing coolant fumes can be toxic so the heater core should be replaced or bypassed. Repair manuals may be available at your local public library if you do not wish to purchase one.

Thank you for responding,
I know about manuals, I also know that they don't relay the amount of frustration or caveats that only "first hand experience" will reveal.

I am just looking to hear from someone who has actually done the work that can tell me what to expect.
Thanks

-10-4, its a heater core....

Be Careful out there.
And remember breathing coolant fumes can be a hazard to your health.
Keep plenty of outside fresh air in there untill you get it fixed.

i agree with all above. heater core. on most cars it requires ripping out the dash to some extent (ooh yeah and that is fun). but there is something else he can do... as a mechanic i dont recommend this, mostly because it clogs things up. but radiator fix (in a small amount like half the bottle) might do it. ive heard of it working... heck we have a 91 skylark the heater core was leaking, and thats what we did , never caused a problem. but when i got a leak in my radiator and i didnt have the cash to replace the 250 dollar radiator in my 90 laser, i put that in and it gummed everything up. crap like no heat in the cabin, over heating of the engine, clogged lines all started showing up.

My fault,
I was hoping for a first hand experience with this make and model.
I have done my share of heater core replacements both personal and in the shop.
Thank you for all the responses though. It is great to see so many eager to help,
THANK YOU ALL!!!

Hi Just put new core in my 93 4L about an Hour job Take glove box out Five little bolts pull out of fire wall disconcert two hoses beside receiver dryer then pull out the core from under dash