My 1999 5.2L, V8 Dodge Durango is having a problem with the front window defrost. It takes like 20 minutes for it to clear the window. Also a fog or mist comes out of the heater vents when the vehicle is warmed up. The heater works and the AC works also.
Defrost takes approximately 20 minutes to clear the front window. As soon as I turn it on, it fogs up all of the windows inside. It blows out warm air but is very slow clearing off the front windshield. Also there is a fog or mist that comes out of the heater vents when the engine is well warmed up. I have not had any overheating problems and both the heater and air conditioner work.
Check that the air conditioning compressor is running when defrost is selected. If it is, the condensate drain tube may be plugged. That will allow water to accumulate under the heater core and it will vaporize when heated and blow up on the cold windshield where it will condense and cause that fogging. The drain tube ends in a 4" long rubber hose with a 90 degree bend hanging down from the passenger side of the firewall under the hood. Squeeze it to open it up and dislodge any debris.