So like I said before I don't have any experience with this kit or installing AC in general to a heater-only TJ, but if I had to guess based on your manual I'd say you need a difference vacuum harness, or the vacuum lines need to be rerouted.
Look at my post above with the vacuum diagrams, that a representation of the harness & where they go to the different actuators & vacuum ports. For example, port G on heater only model isn't used, on the AC model it goes to the recirc door actuator (which you don't have). Also ports D/F on the heater only model go to the same actuator, but they don't on the AC model.
I don't know if this kit is designed to work with a heater only vacuum harness, but in any case the system will default to defrost whenever there's a vacuum leak or something isn't hooked up right in the vacuum circuits.
This is all out of your manual BTW, you can head over to the TJ Resources sub forum & get yourself a free copy. The AC/heater control section starts on page 24-16