windows fog up when heater is on

and yes it the heater core it does not cost much to replace the heater core by itself(100 150)more or less for the part itself it the labor that can be long cuz you have to remove the complete dash to replace the core about 8 to 12 hr i would suggest going to a radiator place for a faster service and check your ac unit while youre in there lol

Thanks...I will check with radiator places!

If your AC does not work this can cause your windows to fog up, the AC cycles on these cars to keep the moisture level down. Also remove your cabin air filter if you have one. I find alot of wet cabin air filters that cause foggy windows and a musty smell. I haven encountered a wet window inside during extreme temperature changes during winter on my '96 taurus. If you are smelling coolant, then it is the heater core. You will have to remove most of the dash board, I have done this in about 2 hours. Heater cores seldom fail on these cars, and when they do it is usually because it is plugged up, not leaking.

Thanks for the info...I have an appointment to take it in on Monday to get fixed.

they leak and need to be replaced because with bad coolant it get really corrosive and those heater core have some small place with not a lot off metal so when the coolant liquid get there and a lot older then recommancded it become corrosive and eat the part up that why youre supposed to replace your prestone each .... mile and each year depend on brand and model there is a reason why and ive seen propeller on a water pump almost gone because prestone was corrosive