Heh! What year was it?
It was a '71 I think. Maybe a '70.
I ended up tearing it apart and completely redoing the heating system so MY bug actually did defrost the windshield in winter. But that's all it would do.
I used PVC pipe and built a direct line straight from the heat exchangers to the windsheild with no provisions for heat to any other location. Then I insulated the PVC.
The problem with bug heaters is that the heat source is way in the back, practically under the rear bumpber. Then there are two steel tunnels that run under the car on either side. There is a vent at the back seat people's feet, then a vent at the front seat people's feet, then vents in the dash, and then FINALLY vents at the windsheild. well, as you can guess, by the time you get to the windsheild, there isn't much air left, it all got siphoned off at the last 3 stops. and the dampers on the vents don't close all the way, so theres really no way to turn off the heat to any one location. And on top of that, the hot air is running in a steel channel UNDER THE CAR! The outside is cold and the air in that channel loses temperature pretty fast, so much of the heat just gets wasted. One other tip is those pesky heat exchangers. They go bad pretty easily and they are really expensive to replace. I never did figure out a good way to fix the old ones. All I can say is you gotta bite the bullet and buy new ones or you won't get any heat no matter what you do.
I still had to wear long underwear and wool socks, but at least I didn't have to keep an ice scraper for the INSIDE of the windsheild