The 124, at least the US models, are an expansion valve and cycling switch system. The regulation of the temperature is accomplished by varying the amount of coolant allowed through the heater core along with regulation of the fresh air flaps.

An accumulator system is predominantly used in GM cars, or Euro cars with a GM a/c system.

There are many, MANY posts on this forum regarding this system. Searching on a topic such as 124 a/c will probably result in more threads than you care to read.

Hopes this helps,