Thermostat fan control probe position
 

I am installing a thermostatic switch control for a Spal fan on my 68 230 W110 that heats up in traffic during this hot summer. I am also restoring and reinstalling my Kuhlmeister AC system with new condensor, hoses, etc... I have a Rainbow TS120S-2 thermostatic fan control switch with radiator probe and would like opinions on probe placement. I see some manufacturers recommend placing the probe at radiator inlet, to me this seems incorrect as it doesn't take into account the radiator's efficiency. I want the fan to come on when the radiator outlet temp is too high thus signalling the need for the fan. I want to cool the water before it goes to the engine, not signaling the fan after the excessively hot water has made it through the engine. Thoughts? The fan will also be controlled by a trinary switch on the AC system. Thanks for your help.

The way I read this is "Radiator inlet" which is engine output, which should be correct. Engine input is radiator output (the bottom hose) which would result in the fan only turning on when the water going into the engine is already too hot. These vintage MBs don't like to run at 212°F like modern engines, they prefer 175°F.