School me on electric fan operation

1993 940 wagon with Rex/Regina. How does the cooling fan operate? There is a switch in the radiator that when closed runs the fan on high. What temp should it be closing at? What about lower speeds? I?ve heard there are manifold switches on the ac compressor. But my ac is completely discharged. So I?m assuming with the ac not charged,I?ll only see the fan on high triggered by the switch in radiator. Is this correct ?

The thermoswitch in the radiator usually says the temp on it, very small writing. I don't know about your other questions because I have never had a car with the e fan stock, I add them later and always run them on the high speed. The only thing that affects it is that switch turning the fan on, at least when I've done it.

A 1993 regina car has only 2 on switches for the cooling fan, both of which are external.

Low speed is controlled by a pressure switch in the condenser for when the ac is on. So yes you are correct, you will never see low speed operation without the ac being on.

High speed is controlled by a temp switch in the end tank of the radiator. It will come on around an indicated 225-230F at the thermostat housing. Very very toasty IMO.

It is very easy to tap into either low/high speed signal wire and add a switch if you want an override control over the fan.