Having studied both the parts diagrams and electrical wiring diagram (both linked above), I don't understand how the Oil Temp and fan are separately triggered - the fan should be triggered earlier than the Oil Temp red light as that should only come on when the oil is overheating and the fan has been unable to sufficiently cool it.
There seems to be only one Thermo Unit (21) which would presumably only set one off. But perhaps the Fan Motor Control Unit (20) that it goes to senses the different resistances and can distinguish the lower point of when to turn the fan on and the overheating point when the Oil Temp red light needs to be illuminated.
For the Fan Motor Relay (1
, it looks to have two triggers before it powers the Fan Motor (19).
The first is the Br wire (presumably relay pin 86) looks to have a live 12v+ positive feed that is enabled by the Main Switch (2) - presumably an Accessories or Ignition - this would stop the fan from running when the bike is shut down/off.
The second is negatively triggered by the W wire (from presumably relay pin 85) going to ground (GND) through the Fan Motor Control Unit (20) B wire (GND). This allows the Fan Control Unit (20) to control when it wants the Fan Motor (19) to run by completing the circuit to ground, or breaking it, to start or stop the motor.
The other two wires on the Fan Motor Relay (1
R/W wire (presumably relay pin 30) looks to have a live 12v+ positive feed that is enabled by the Main Switch (2) - presumably an Accessories or Ignition - it actually connects back to the Br wire (that feeds what is presumed to be relay pin 85). The key difference here is that it goes through a Circuit Breaker Fan Motor (17) before the Fan Motor Relay (1
- likely as a protection mechanism to avoid overloading in the event of a failure etc. as I imagine the fans location makes it easy to become damaged or blocked up and fail.
L (presumably relay pin 87) connects to the Fan Motor (19) and provides it with power when the relay has been triggered to activate.
Therefore, since this bike is just used for low tempo, low speed maintenance tasks (weed spray, horse feed delivery, horse poo collection, etc), which don't promote much air flow over the oil cooler radiator, I plan to rewire it so that the fan is constantly running with the bike ignition. To achieve this I think it's simply a matter of adjusting the Fan Motor Relay (1
W wire (from presumably relay pin 85) to go directly to a ground earth. Since the Fan Motor Relay (1
would then have a constant ground earth connection on the W wire (from presumably relay pin 85) the relay should the activated and therefore power the Fan Motor (19) when ever the first trigger on the positive Br wire (presumably relay pin 86) is enabled by the Main Switch (2) - i.e. when the bikes key is turned to On it should start. The second trigger on W wire to the Fan Motor Control Unit (20) is removed - so the Fan Motor Control Unit (20) no longer has control of the Fan Motor Relay (1
I'm no auto electrician so very interested in anyones opinions/comments if I've misinterpreted any of the above...