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Discussion Starter #1
I installed a manual fan switch which will run the fans anytime eng on or off. I've included some poor pictures (sorry but the site won't handle really good ones) of the fuse, relay, switch housing and switch installed. It's between the throttle clamp and switch housing. Works the nuts. Hit the switch and on they come. I'm posting it because people had mentioned they'd like a manual switch.
 

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awesome! i knew it would work great!

congrats on the install! looks good!
 

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NICE! Its about time someone did this. It is hard to tell where you are wired into. Would it be possible to write out what exactly you did. Looks great and thanks for sharing. :yo:
 

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Lee, see the little relay that you have tie wrapped your big one too? thats the original fan relay............. :)

Nice bike by the way, any pics you could post?
 

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Discussion Starter #6
I studied the wiring diagram for awhile and wanted to tie the new circut into the existing fan relay. Can't be done if you want to run the fans with the eng shut down. That ign switch appears to be a batt disconnect 'cause I couldn't find +12v anywhere when it was off. So I ran 14ga wire ( I'm going to add another fan and need the size in the feed from the batt) from the + post over to the right side and into a fuse holder (15amp) which you can see in the pic. From there it follows that anaconda of a wiring harness up to the stock fan relay. You can see it (blue wire) in the pic. It either goes under the rubber "clamps" or is tie wrapped to secure it. I got a relay (see pic where it's fastened to the stock one) and ran the blue into the hot feed post. I also added a jumper from it to one of the relay coil posts. Two yellow wires come off the hot out post and are spliced into the fan wires. The fans are wired backwards so they'll rotate in right direction so the hot wires from the relay go to the black gnd wires on the fans. No ground wires are needed from the fans as the existing ones (blue) take care of that. The switch is a mini spst from Radio Shack. You can use them as the relay coil draws very little current and being so small they're easier to mount and don't stand out like some big toggle would. One wire from the switch goes to the remaining post on the relay and the other is grounded to the screw that holds the front brake light switch to the lever clamp. I machined a little housing out of Alu and painted it satin black to match.

So when the switch is flipped it completes the relay coil circut to ground which actuates the relay and sends power to the fans which goes through the motors and to ground via the existing ground wires and on they come. When in traffic you can turn the fans on BEFORE the stock relay does and when you shut down you can run the fans without turning on the ign or running the engine. I do not think that it will make much diff in traffic with the current fan arrangement but when I get the third fan on there and seal the gaps between the fans and the rad, along with Muzzys on all three I expect to see the temp plummet when I hit that switch. F---- better after all this. Now all I've got to do is find a way to get the air out of the fairing. Right Mike? Actually I think there's enough open area that it won't be a problem.

Sorry this is so long. If you decide to do it and need help just holler.
 

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Thanks, i'm going to leave mine std on the wiring, the only time I ever run the fans without the motor is either in traffic when I just hit the kill button (later bikes also kill the headlamp unless the motor is running, or at home after a ride whilst I take my lid and leathers off)

One thing you may want to look into is early euro bikes had a headlamp on/off switch on the LH switch gear where the blank is now fitted, I have never studied the wiring, but did think about using that switch for other purposes :naughty: like a hidden power switch for a laser jammer :jsm:
 

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Discussion Starter #9 (Edited)
Mike- Thanks for the tip on the switch blank. Maybe for future use?

Peter- The whole point of this project is to try to cool down the engine while in traffic and to bring down the coolant/engine temp after shutdown without having the ign on. I think it's a worthwhile effort but who knows? I may get all done and find it doesn't do squat. It's called "not having a life". You wanna' see some heat on your leg? Sit on a Duc 1098 with the full Termi exhaust in traffic. Now that's some serious heat.
 

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Nice idea.

Has anyone ever thought of painting their radiator(s) black? That should help them work more efficiently. I don't know what gains could be expected though.

Si
 

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As it's a mechanical water pump as standard, I can't see any real benefits to running the fan while the engine is off as all you are really achieving is cooling the water/coolant within the radiator and not much else.

I'm sure having manual control of the fans and bringing them on earlier will have some benefit in dealying the temperature rise but I can't help but think that sourcing an alternative thermal switch would be a better road to take?

TBH, I haven't looked at it too closely lately so it may not be as simplistic as that. I know the original 750s used a simplistic thermal switch to control the fan relay, and I believe fan relay control was later moved to the ECU but, is there still a thermal switch or thermistor dedicated to fan control or does the ECU determine when to turn the fan on/off from the ECU's general engine temp sensor?
 

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Hartley Hare said:
As it's a mechanical water pump as standard, I can't see any real benefits to running the fan while the engine is off as all you are really achieving is cooling the water/coolant within the radiator and not much else.

I'm sure having manual control of the fans and bringing them on earlier will have some benefit in dealying the temperature rise but I can't help but think that sourcing an alternative thermal switch would be a better road to take?

TBH, I haven't looked at it too closely lately so it may not be as simplistic as that. I know the original 750s used a simplistic thermal switch to control the fan relay, and I believe fan relay control was later moved to the ECU but, is there still a thermal switch or thermistor dedicated to fan control or does the ECU determine when to turn the fan on/off from the ECU's general engine temp sensor?
There is one definate advantage of running the fans with the motor turned off and that is to cool the exhaust manifold and stop the radiated heat mellting the plastic fan blades.

The 750 with the thermal fan switch was the original single rad bikes, since then it's been done via the ecu
 

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Discussion Starter #13
I'm not sure about this so no moron talk. I think with the engine off there's still some coolant circulation due to temp diff. Hot rises and cold sinks sort of thing. I had a chat with a guy at Muzzy's and he said running the fans after shut down is a good thing to do. So WTFDIK? There's two temp probes, one in the rad and the other in the engine. I believe the rad one is for the inst temp and the eng for the fans. I know I jumpered both of them and the fans still wouldn't come on. Also there's a blck/wh wire running from the fan relay coil right to term #20 on the ECU so I think it's calling the shots.
 

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mikef4uk said:
There is one definate advantage of running the fans with the motor turned off and that is to cool the exhaust manifold and stop the radiated heat mellting the plastic fan blades.
Definately a valid point there Mike. Although, installing a set of metal fan blades while being more expensive would also be a more elegant solution to that particular problem.
lee said:
I'm not sure about this so no moron talk. I think with the engine off there's still some coolant circulation due to temp diff. Hot rises and cold sinks sort of thing. I had a chat with a guy at Muzzy's and he said running the fans after shut down is a good thing to do. So WTFDIK? There's two temp probes, one in the rad and the other in the engine. I believe the rad one is for the inst temp and the eng for the fans. I know I jumpered both of them and the fans still wouldn't come on. Also there's a blck/wh wire running from the fan relay coil right to term #20 on the ECU so I think it's calling the shots.
Indeed, when the coolant is not being circulated by the water pump there is some level of convection cooling to be had. I'm just not overly convinced that the convection cooling has any real world effect.
 

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Discussion Starter #15
Oh I'm sure it doesn't. But maybe when one adds up all the little effects it's enough to make some difference.
 

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Somewhat smart a55 remark coming...Okay, here's an easy and very inexpensive fix to both problems; traffic heat and post ride cool down.

1. Don't ride in traffic.
2. Post ride - point a house fan at the front end of the bike for 15 min.
 

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lee said:
I'm not sure about this so no moron talk. I think with the engine off there's still some coolant circulation due to temp diff. Hot rises and cold sinks sort of thing. I had a chat with a guy at Muzzy's and he said running the fans after shut down is a good thing to do. So WTFDIK? There's two temp probes, one in the rad and the other in the engine. I believe the rad one is for the inst temp and the eng for the fans. I know I jumpered both of them and the fans still wouldn't come on. Also there's a blck/wh wire running from the fan relay coil right to term #20 on the ECU so I think it's calling the shots.
The rad 'probe' supplies temp measurement to the dash, the engine one does the same for the ecu :)
 

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I studied the wiring diagram for awhile and wanted to tie the new circut into the existing fan relay. Can't be done if you want to run the fans with the eng shut down. That ign switch appears to be a batt disconnect 'cause I couldn't find +12v anywhere when it was off. So I ran 14ga wire ( I'm going to add another fan and need the size in the feed from the batt) from the + post over to the right side and into a fuse holder (15amp) which you can see in the pic. From there it follows that anaconda of a wiring harness up to the stock fan relay. You can see it (blue wire) in the pic. It either goes under the rubber "clamps" or is tie wrapped to secure it. I got a relay (see pic where it's fastened to the stock one) and ran the blue into the hot feed post. I also added a jumper from it to one of the relay coil posts. Two yellow wires come off the hot out post and are spliced into the fan wires. The fans are wired backwards so they'll rotate in right direction so the hot wires from the relay go to the black gnd wires on the fans. No ground wires are needed from the fans as the existing ones (blue) take care of that. The switch is a mini spst from Radio Shack. You can use them as the relay coil draws very little current and being so small they're easier to mount and don't stand out like some big toggle would. One wire from the switch goes to the remaining post on the relay and the other is grounded to the screw that holds the front brake light switch to the lever clamp. I machined a little housing out of Alu and painted it satin black to match.

So when the switch is flipped it completes the relay coil circut to ground which actuates the relay and sends power to the fans which goes through the motors and to ground via the existing ground wires and on they come. When in traffic you can turn the fans on BEFORE the stock relay does and when you shut down you can run the fans without turning on the ign or running the engine. I do not think that it will make much diff in traffic with the current fan arrangement but when I get the third fan on there and seal the gaps between the fans and the rad, along with Muzzys on all three I expect to see the temp plummet when I hit that switch. F---- better after all this. Now all I've got to do is find a way to get the air out of the fairing. Right Mike? Actually I think there's enough open area that it won't be a problem.

Sorry this is so long. If you decide to do it and need help just holler.

When I do, I might need some help. I will study this post and diagrams, should be able to do it. I wont be wiring in another fan though.
Thanks Lee!
 

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Old thread bump - sorry. But i want the manual fan switch for hot weather traffic riding only. I plan to leave my key on for cooling hot stuff down so I dont need to have the option to turn the fans on with the switch when the bike is off.

I cant find the fan relay wiring diagram here anywhere but I seems like I could just "splice" the switch inline with the proper wire on the relay and achieve the manual switch upgrade?

Im a mechanical engineer, because I didnt care about wiring at all. So now I sound like a noob.

On another note - why on earth doesnt the maintenance section have all the cool mods sticked?
 

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The fan relay is where your right knee is sitting on the bike,the relay has a rubber strap securing it to the fuse block.At the relay you will see a black/white wire,that is the wire you need to splice into and run the wire to the switch,then to earth,and thats all there is to it.
 
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