280GE air conditioning - help re temperature sensors required

There are two temperature sensors on the wiring diagram.  I think one of these is on the engine block and the other on the drier.  Both control the auxiliary electric fan.  As my replacement drier has two ports rather than the three of the original unit  (price difference is over £300) I have replaced the sensor on the drier with a manual switch on the dash. Does anyone with a superior knowledge of the 280GE's air con think this is a problem and what sort of temperature on the engine is supposed to operate the fan  (normal or very high - i.e. should this cut in routinely when the air con is switched on and the engine is warm or only when the system is stressed at high temperatures?

I would be grateful for clarification from any air con gurus.