Answer: I never would have known the answer to this question had I not just bought a 1974 Bricklin myself and had the same problem. The compressor should not run any time that the ignition is turned on. Determining where the problem lies may be a bit of an issue because there are several possible causes, and at least as many solutions that have been tried by Bricklin owners over the years. Because so many owners have made modifications over the years, there is no way for me to tell how your car is configured.
Since you say that the doors function perfectly, I’m going to assume that there are no air leaks (which could keep the compressor running) and focus on the electrical possibilities, which are the most likely cause. It sounds as if the compressor and the pressure switch (which is supposed to turn off the compressor at a pre-set pressure) are wired directly to the high current side of the starter solenoid, which is “hot” all the time. This seems to be the way that most of these cars are wired. It is also likely that the pressure switch is faulty or missing, which would explain why the compressor keeps running.
After much research on my own car the consensus is that the best way to operate the compressor is with its own relay that is energized when the ignition is turned on. There is even an integrated relay/pressure switch that is available for this purpose. By wiring it this way you will not have to disconnect the battery as it will not have an electrical source as long as the ignition is turned off. There should be a switch under the passenger side of the front bumper that originally activated the compressor. You can wire this switch as an “emergency bypass” to activate the compressor. This might be necessary if the air system develops a leak and you cannot open the doors, allowing you access into the car to turn on the ignition switch. If this were to happen, I’m not sure AAA would be much help.