The reason you put a fan switch in the bottom of the radiator rather than in the block is the fan is only used to cool the radiator water not the water in the block
The thermostat is the item that controls block temperature.
when the switch is in the radiator, which is what the fan is cooling, and it gets to the desired temp the fan will switch off
When you install it in the block the thermostat and the fan switch will be fighting each other for control.
The radiator water gets colder than necessary then goes into the block when the thermostat opens and you get fluctuations in block temperature which may cause damage to the block
Scooter33
The thermostat is the item that controls block temperature.
when the switch is in the radiator, which is what the fan is cooling, and it gets to the desired temp the fan will switch off
When you install it in the block the thermostat and the fan switch will be fighting each other for control.
The radiator water gets colder than necessary then goes into the block when the thermostat opens and you get fluctuations in block temperature which may cause damage to the block
Scooter33