1965 Mustang Fastback A C leaking at passenger left

Hi Cliff, and welcome to the forum!

There is a rubber drain hose attached to a nipple at the rear of the bottom of the A/C unit closest to the passenger's feet.

This hose comes loose, cracks, or even clogs where it exits through the floorboard. Inspecting this hose will likely reveal the problem.

Sometimes the drain nipple itself will clog and the pan of the A/C unit will fill with water and splash out. The drain can be cleaned out by removing the hose and inserting something to clean it out.

As I recall, the entire bottom half of the A/C unit is essentially a catch basin for the condensation.

If the drain tube is sealing to the bottom of the A/C unit, doesn't have a hole in the side of the tube, and is clear to drain, there should not be any getting on the floor.

I suppose the bottom of the A/C unit could have a crack in it?

I think these are made of fiberglass?

I'm thinking that the 66 Mustang I had that came with A/C back in the day had a spring-type compression clamp on the upper end of that hose.

It has been so long now. I can't be sure, but I seem to recall having problems with my hose leaking because the clamp pinched through the thin rubber hose.

I owned it from 67 through 72 and rememberl dealing with that hose on multiple occasions.

I have an A/C kit for my 65, but must admit that it doesn't cool very well in that box on the shelf in my garage.