Fan operation.

Paul Bryant

Living Legend
Joined
Jun 17, 2008
Messages
3,226
Location
Hamilton. New Zealand
Ride
2006 Rocket
So i have the bike sitting, running at idle for 15 minutes.
The fan kicks in as I expect it would. What I am surprised about is I kill the engine with either the kill switch or by turning the key, I then simply turn the key or kill switch back on but don't start the engine.
Now as the engine/coolant is up to fan operating temperature, I expected the fan to immediately switch back on, but it didn't.
Is this what you Guys would expect ? To me the Engine is now sitting there, not running with the overall temperature (reasonably) high I would have thought that the fan should be going.
Of coarse I realise that with out the engine running, the water pump is not spinning.

I've done this several times with the same result.
 
I thought I had a thermostat problem with my old Trophy that did the same.
I checked the temp (with IR at the lower and upper radiator) and if the trophy was over 190 the fan came on regardless of the key position.

After too much analysis I just let it be and it ran fine. Hot from the updraft, but fine.

I flushed the system and did add some "Water Wetter" to the radiator mix (follow directions) and the temp didn't rise as fast, but it came on at 190 no matter.

If you are really curious then record the temp when it comes on from cold and see when the fan starts.
I believe this is adjustable in Tune ECU.
 
Paul the fan turns on when it reaches 103 C say and has low temp to turn off. It could be after losing power the ECU sees the temp as below the turn on point so it doe snot come back on. IS the temp below the shut off probably not but the ecu still thinks it is not heated up enough yet to turn on. Just thinking out loud!!!
 
When I think something is over heating, I think of my ex-wife. Just the thought of her cold heart makes the sun a little cooler, imagine what it will do for an over heated bike...
 

Thanks Scott, I've not done any temp checks, I don't have the gear, I just thought it was a strange thing the way it behaved.
 
Paul Bryant said:
Thanks Scott, I've not done any temp checks, I don't have the gear, I just thought it was a strange thing the way it behaved.
Click to expand...

My guess is the ecu software is looking for conditional statements If the parameter is met like 103C turn on temp it turns on. If fan temp is less then say 99C shut fan of. But to meet this conditional statement the ecu first looks to see if the fan is on. It like parametric programming only not as sophisticated.
 
While "Engine runs" = TRUE:
 
I'll go with Warp9.9's comment here. The fan comes on at say 103C as its programmed to. But the computer will have a programmed "dead band" whats called a hysteresis. Say its 3 degC, the fan will turn off at 100C this is to stop the fan going "on/off...on/off", and ruining the electric fan motor, it would also be annoying.

Whats probably happening here is the fan starts at 103C and then the motor is turned off. The motor may at this point be only 102C but the computer has reset and is again saying only start at 103. It doesn't know that it was running before the switch off. If the motor was still over 103 I think it would come back on.

This is fairly basic process control but adequate on a vehicle.
 
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