is it worth it to replace the blower regulator with an used unit?

Prior to my blower motor not working, i recall the speed no longer worked as well and it didnt seem to cool as much, maybe just due to the speed of the blower.

Today we had finally a sunny day so i ventured to replace my blower with a pulled one from a diff vehicle.. which is probably as old as mine but works. (and it does work but it squeeks a lot lol), anyways.. i also purchased an used regulator which has yet to arrive.

I figured I would replace the fan today to learn and see how the process is, and then just redo it later, now I am wondering if maybe i should just buy a new behr motor and stick with the used regulator that i should be getting soon.

Which reminds me, if blower was working, and speed selector was working, if the car was low in freon what would I experience? not so cold air, when set to cold?

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89 300E - 240k +