I don't know if this applies to all years of 124s (probably does) but my '90 automatically switches over to recirculate as the temp. of the outside air climbs. You can hear the change-over as the vacuum door moves. When it is 90+ F outside, the air from the vents is VERY cold (R12). Eight years ago the evaporator was replaced along with a new expansion valve and all vacuum actuators. Compressor is original and the system still has a full charge these eight years later. The A/C in a 124 will do a very good job of cooling when everything is operating properly. Several years ago I also added a "Cool Harness" that makes the electric fan come on at 93 F instead of 100 F. This helps in hot weather, especially in stop-n-go driving. I just don't like seeing that needle go above 100 F.