Testing the AC on my '71 Sovereign

[Kait]

Hi,
I've been told by the previous owner that the AC unit worked not too long ago, but the wall mounted control switch is missing and I'm not able to contact them. I want to be able to test it and also to run the thing if it does still have life in it. Does anyone know where I might get a new switch or if there is a way to override to be able to test the AC unit without a switch?

I have 4 wires coming out of the wall where the switch used to be.
They are Red, Brown, Green and Black, in case that's helpful.
One of the four has 24 volts and the others are not active.
Thanks so much!

[J. Morgan]

I don’t know the colors, but for the remaining three wires apart from the 24v feed, one wire will be for the compressor, (RC), one will be for low fan. And the other for high fan.