Hiya All,
I thought it might make for some closure on this subject if I were to update it with how I went about solving my original problem. But before I do that, I'd like to thank all the folks who contributed their ideas to this thread. I originally asked about heater and defroster settings to best combat the fogging over of the windshield in cold and wet weather only because I was looking for an easy answer to my situation. For anybody out there who finds themselves in a similar situation to mine, I would strongly advise that they try out the suggestions above. You just might find that your problem is easily solved
Mine, however, was not so easily solved. After trying out the suggestions above and getting little success, I determined that I was going to have to pull apart the heating system (from the heater channels up) and examine everything. Here's how it went along with some observations.........
1. Footwell vents: Mine had no insulation on the flapper tongue that protrudes into the heater channel. As a result whne the the flappers were moved to the heat position, hot air would blow under the flapper. This resulted in less heat at the footwell vents and a "bleed-through" of hot air which (because of a condition described in hoses below) caused fogging of the windshield. I used a foil faced foam and cut it to fit the heater channel. Afixed that to the flapper with 3-M spray adhesive. Now, when the vent is in the heater position there is NO air at the defroster vents.
2. Hoses: Although the original paper/foil vent hoses looked good from the outside, it was a much different matter on the inside. The large 47mm hose which extends upward from the heater channel is actually a hose with a double-wall build. From the outside in it is paper-foil,and paper again. The inside paper layer had become wet and had bubbled, blistered and deformed so as to restrict the amount of air moving through it. Removing and installing a replacement for this hose was not a fun job. I wound up enlarging the small access hole at the bottom of the A pillar interior. I honestly don't see how this removal/installation can be done without enlarging the hole.
The 32mm paper/foil hoses above the three-way connector were in similar condition. The hoses leading to the corner vents were especially wet and moldy. Yuck! I replaced all the hosing (except the plastic hose leading to the center vent) with flexible aluminum hosing.
Fresh Air Box: This I cleaned out again. The drain hose was cleaned out also. I checked and replaced the seal around the top of the box. The flappers had been recovered last year with the same insulation I used on the footvent flappers. They were in good shape. However I found that the passenger side control wire had come loose at the "bridge" just behind the dash, so that was reconnected.
The results have been pretty dramatic. I now have a strong (well...strong for a Bug) flow of air at the windshield vents. I have no problem keeping my windshield clear whether the car is moving or idling at a stop sign. This is also the case with me being wet and hot after a run on the track. In other words, the defrost is now working as it was designed. I'm quite pleased with the way this turned out and I hope my experience might help somebody else down the road.
Mike
1970 AS Bug
1970 Bus - The Ruptured Duck
