too much heat

[kchemers]

89 300TE Car has automatic climate control, set the temp the blower goes on cabin heats up fan switches to low but won't maintain constant temp, cabin gets very warm. If I turn the temp down to the blue, fan kicks in air moves to the dash vents but they blow hot, only way to control temp of cabin is to turn the system off and wait for cabin to cool down, then turn system back on doesn't matter if I operate in economy or regular mode. System just started acting up was operating perfectly, cold a/c perfect heat, did I spring a freon leak????
Thanks kchemers