I have researched all the posts that I can find on heater problems but have not been able to find one that covers my problem. The system does not leak, has a new thermostat, gets to 90 degrees Celsius on the temp gauge and my Scangauge and does provide some heat to the cab. When I switch the control to the de-mist setting my windshield and side windows fog up and, even with the fan full on, never really clear. I cannot find any sign of leaking into the cab from the heater core and there is no smell of anti freeze. I'm not sure exactly how hot it should blow into the cab so I'm not sure if I'm getting full heat output. Anyone got any suggestions of the cause and a fix?

 

If you're windows are fogging up, it sounds like you're somehow on "recirculate" with regard to the HVAC controls. My Jetta TDI does this if I set the defroster and have the "recirc" button engaged. Might be something with your "blend door", try a search on here for that.

 

Another thing to look at besides the blend door is possibly a clogged heater core....fastest way to check that would be to feel the hoses that supply coolant for the heater....just feel them to see if they are roughly equal temps.