Coolant leaks out when I turn AC on
My car has 90000 miles.
My car has an automatic transmission.
Coolant leaks are generally noticeable with or without the AC on as the AC should not have any impact on the coolant system other than the fact that the engine works a bit harder when the AC is on. You may want to have the leak inspected to verify that it is in fact coolant leaking and not just condensation from the AC system, which is very common on almost any car, especially during a hot day.