With reference to a long thread on electric fans,
https://ozvolvo.org/discussion/3316/850-electric-fan-in-240/p1
I supply a
thermo fan circuit diagram of mine that does two things:
1. Fan can be manually switched ON or OFF an any time (but naturally not OFF if thermo switch is heat activated to be ON)
2. Fan auto starts when thermo switch signals it to be ON
The circuit is tried and tested. Hight current side should use thick wires 2.5mm and up.
Note:
Supplied is figures indicating the huge current draw of thermo fans.
eg 16" for flat blade types 11.5 amps running and 22.5 on startup.
I wrote to PWR radiators in Brisbane as they use SPAR brand fans. The curved (S) blade fans flow significantly more air than the straight blade, but curved type draws significantly more current than straight (bit less than double the amps).
So on a Volvo engine, a monster flow rate is not required (compared to an old chev V8 with a half blocked radiator)