Thermo Fans come on when engine cold...which sensor does this point to?

[Billy22Bob]

1995 TS 2.6EFI Sedan 120k km

When I started the car yesterday I noticed the thermo fans came on immediately.
I'm just wondering which thermo sensor signals the ECU to turn these on. I'm figuring it needs replacing.

[ac1176]

Workshop manual says the fan is operated by a thermoswitch located at the bottom of the radiator. Not controlled by the ECU. Could also be the fan motor relay is faulty.

[Billy22Bob]

Thanks.
Sorry for not looking.

I've just flushed the radiator system x10 to get rid of rusty water and refilled with coolant.
There was some residue lining the pipes which I descaled and cleaned properly.

Given the thermosensor if closed circuit runs the fan - as indicated in the test procedure - I suspect my thermosensor is closed circuit, rather than the relay. Will pull and check today.