Have you cleaned the inside of the windshield real good?

Have you tried running the ac when it fogs?

 

Hi Azdude,
Yes, I've done both! I had to run the A/C and have the windows cracked open too!

 

Check that the HVAC is set to take in fresh outside air, not to RECIRCulate moist, inside air.

 

If it leaves a residue on the inside glass it could be a heater core leaking. Check that your coolant level has not changed. Otherwise as stated above in moist air you need to be using fresh outside air and AC when very humid.

 

Does the glass fog up inside or outside?

If you run the window de-fogger for too long it will cool the glass enough for condensation to build up on the outside.

 

Just a thought for something to check ...
I've got this problem on my 2011 LX, need to fix it in the next few months ...

There is a problem with one of the HVAC flapper controls that directs which vents the air comes out of. My OBD2 code is B1239, and I do believe it.

Somehow it is stuck in a position where the air cannot be directed to flow up over the inside of the windshield, as it should be able to. In foggy atmospheric conditions, this means the windshield will fog up, and the solution is to basically heat up the entire car interior so the inside of the windshield is warm. The only problem I've found with this workaround is the sound coming from the rear seat passengers, but it is something I'll need to fix.

So for you, I would check to see that air comes out at the base of the windshield when you've got the HVAC set to defog / defrost / etc.

 

Turning on the defrost will automatically engage the A/C compressor. If you have an EX and above the A/C cycles all the time, even when you have the temperature set high enough to heat. The A/C button has to be turned off manually if you don't want it.

 

Mine fogs up as well when my cabin air filter needs to be changed

 

Echoing #4. Check coolant level and see if you can smell coolant in the cabin. A leaking heater core will definitely create its own weather system in the van.

 

check the cabin air filter to see if its plugged up?
did that in my civic & wahhhlaaahhh!