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Fan switch
DRCorsa - 25/1/12 at 10:46 AM

I am trying to figure out how the fan switch is gonna work in my BEC. I will use the usual suspect Polo radiator.
I have 2 different options for a fan switch:

1) Either use a M22x1.5 fan switch to go to the Polo radiator with the right temp range
2) Or make a M22x1.5 adaptor and bolt the stock bike fan switch on it.

If i go to option#1, how will i connect the switch to the engine's wiring, so the switch will receive the ECU fan on-off signal?
If i go with option#2, how can i connect the stock bike fan switch to my radiator fan?

I am somewhat confused on that problem, so i will ask in a few words:
How do ensure that your radiator fan receives the ECU on/off signal?

loggyboy - 25/1/12 at 10:55 AM

Is the fan switch ECU led? the normal way is the switch just turns the fan on when the switch says its hot enough. The thermostat will do the temperature monitoring of the engine, you just need the switch to kick in when there is not enough airflow for the rad to work alone. keep it simple - polo switch, wired direct to fan, and consider an overide swith from the dash incase you want the fan to be on more often?

britishtrident - 25/1/12 at 11:36 AM

If you are a making an adaptor block use an M14 size switch as used on some Volvos, BMW and Renault ---- M14 taps are much cheaper. than M22

DRCorsa - 25/1/12 at 11:50 AM

quote:
Originally posted by loggyboy
Is the fan switch ECU led? the normal way is the switch just turns the fan on when the switch says its hot enough. The thermostat will do the temperature monitoring of the engine, you just need the switch to kick in when there is not enough airflow for the rad to work alone. keep it simple - polo switch, wired direct to fan, and consider an overide swith from the dash incase you want the fan to be on more often?


In the original setup, there was only a temp sensor fitted to the radiator, just to give temp readings to the dash. There is another temp sensor on the engine block, the signal of which is used by the ECU.
I assume that i can use a regular Polo fan switch and connect it to the radiator fan, so this switch will turn the rad on and off.
I am pretty sure that the original bike fans were ECU controlled (probably using the signal of the temp sensor on the engine block), but i suppose i can ignore the plugs originally connected to the fans and rely solely on the Polo fan switch, right?

In a few words. I will normally use the M22x1.5 fan switch to my Polo rad and then i have to find a way to connect the original temp sensor somewhere to the cooling system, maybe attaching it on one of the alloy T-piece i will use.

[Edited on 25/1/12 by DRCorsa]

loggyboy - 25/1/12 at 12:16 PM

Im no BEC expert, but that seems logical to me!

adithorp - 25/1/12 at 12:26 PM

What engine is it? need to know that to comment on option2

If you use a thermo switch (option1) in the rad then just feed a fused 12v feed to the swiche then to the fan then to earth. The fee can be ignition switched so the fan would stop when you switch off or perminent live which would allow it to continue to run after switching off untill it cools.

DRCorsa - 25/1/12 at 01:32 PM

quote:
Originally posted by adithorp
What engine is it? need to know that to comment on option2

If you use a thermo switch (option1) in the rad then just feed a fused 12v feed to the swiche then to the fan then to earth. The fee can be ignition switched so the fan would stop when you switch off or perminent live which would allow it to continue to run after switching off untill it cools.


It's not the most popular engine out there. It is a '07 MV Agusta F4 1000!!
I am sorry but i have to correct my writings regarding option #2. There is no fan switch on the engine. There are only 2 temp sensors. One goes to the bike radiator and sends temp readings to the dash and the other is fitted on the engine cyl.head which sends a signal to the ECU. I assume this signal is being used to alter the air/fuel mixture as required and also to turn the fan on and off. The bike's workshop manual is not the most descriptive and detailed one out there.. but this is the logical explanation i can give as to what the second water temp sensor actually does.

As i see it, the most simple solution is to use a thermo fan switch on the Polo rad for the fan operation control and then fit the original temp sensor (placed at the radiator on the bike setup) somewhere on the cooling system (ideally close to the thermostat i assume, to get more realistic values of the temp of the water) in order to have the temo reading on the dash.

But the electrical plugs of the bike's wiring loom will not be used. I know it's unlikely, but would this cause any problems to the engine's operation?

RK - 25/1/12 at 05:37 PM

Caveat: I have a CEC. I have had manual switches, and I've had my fan on all the time. The latter isn't very good, and the former is a bit dangerous, in case you forget to turn it on. I have since bought (off Fleabay.co.uk, as it turns out) an automatic thermal switch that goes into the upper rad hose on my Nissan. This goes to the rad, +ve fused. The rad is already earthed. Should go on at 90 C, and off at 80 C. It was the easiest solution that had potential to keep me out of trouble!

I can't comment on whether not using engine plugs will affect the ECU operation. Shouldn't should it??