1987 Ford Thunderbird Car keeps draining the battery.

Electrical problem
1987 Ford Thunderbird V8 Automatic

I have a 1987 Ford Thunderbird that keeps draining the battery.

I replaced the battery and in a few days the brand new battery is dead.

How do I find out what is draining the battery?

The power door lock switch is not working but all the fuses are good. Could this be draining the battery?

The car has a clock in it, but I didn't have any problems before so I don't think it's the clock.

Could there be a short somewhere.

How to I find what is draining the battery?

Thanks