There are footwell blowers on both side of the car. The engine compartment blower has to be working (and it is) and there is a large relay that has to allow the footwell blowers to run. I am pretty sure my relay is not working. The 911 tech forum has an ongoing thread on how to fix it. I have posted in that thread. I think there is a simple (sort of) way to "fix" the relay as they are not available anymore.
When I took my relay out I saw this corrosion and thought I had found the problem. After 36 years and 182,000 miles it was the first time that relay had been pulled. The corrosion was not the issue. But I fixed that issue anyway.