You have a convertible. You can take it out even on the hottest days.
I have a '69 convertible with factory air, and the only time I've ever used the air is at the Woodward Dream Cruise on one day that topped 90 and I was sitting in the hot August sun idling for an hour at midday.
With the top up, the air conditioning is not all that effective. With the top down, you don't need it.
Vikki 1969 Goldenrod Yellow / black 400 convertible numbers matching
