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Bypass your radiator fan


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  • Forum CEO

Fan Override switch.

The purpose of the switch is to be able to manually turn on the radiator fan. ?I did it out of necessity since my fan thermo switch wasn't working properly and I didn't have $50 to get a new one at the time. ?Priorities prevented it, so I took some wire a few connectors, a switch and wired up a bypass.

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It is a ground trigger switch, all it does is ground the fan power, it is tied into the existing thermo switch so that will still work. If you take the power lead off ?the thermo switch and touch it to the body of the radiator the fan should come on, thats how it works the thermo switch gets hot and the circuit is completed.

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Unplug the female connector from the thermo switch on the left side radiator, It is actually on the radiator threaded into the radiator.

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I made a wire extension that male connects to the female connector, the other end is a female that goes back on the thermo switch its a female connector

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Its only about 2 inches long and is just an extension, I used a tee spice in the middle of it to be the ground source

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Here is the connections to the switch, one end is tee spliced to the extension wire the other is connected to a ground source on the frame.

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This end is the ground connector it is run from the manual switch to a ground

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I made it so I can pull the whole thing out without much trouble no splicing to the original wires.

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You can see where the manual switch is located and where I grounded it (a common ground buss)

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Guest RedFlyer

Ya know, I promised myself that I was going to try and not embarrass myself as much any more, and here I am, right at it again.

OK, I've got to ask:  Why would we want a radiator fan by-pass switch??

It seems to me, with my limited experience, that we would in fact want a SECOND radiator fan, not a way to shut off the only one we have.

I've got my flame resistent suit on now, so feel free, go for it!!

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  • Forum CEO
When I was syncing my starter valves my motor boiled over, I had a burned out fan fuse.  I replaced it and then started up again, the fan would not come on till it reached 260 degrees.  Hell with that I will turn it on myself!  I need to replace that thermostatic switch, but even when it was running right it would not come on till it was 215f , I just want to be able to turn it on no matter what.
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Guest Colorado

THE TEN TOP REASONS TO BYPASS YOUR RADIATOR FAN

1.  Because the wind blast throws off the balance of the bike.

2.  It takes 0.0000201 horsepower to produce the extra electricity required, which robs 0.000107 f/s2 from bike acceleration.

3.  It doesn't work anyway.

4.  You've attached the fan to your reg/rec.

5.  Because your sidecar passenger asked you to cut out the hot air.

6.  So you can add another switch to your Inspector Gadget mobile.

7.  To cover up the hole you drilled in your frame to install the blue neon bulbs.

8.  [Add your own.]

9.  [Add your own.]

10.  [Add your own.]

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  • Forum CEO
The switch does not bypass the radiator fans normal operation cause the circuit is still the same, however with the bypass I can turn it on whenever I need it. All that it does is bypass the thermo switch when I turn it on, so the fan goes on. The way I wired it the fan will still go on if the thermo switch kicks in. Like I said before it was not coming on until the bike was already well over the normal operating temp, I need to replace the oem switch, but the dealer does not carry them in stock, at least this way I can turn it on for the $2 I paid for the parts. The replacement OEM part is $40 and it takes at least a couple of weeks to get the part. The manual switch was already on my dash, from an old project I took apart and rewired.
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FWIW, I did the same mod on my dear departed '86 and it worked great for when you got stuck in traffic. Switch the fan on BEFORE the motor gets hot. It seems to help if you get a jump on the heat.
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Guest RedFlyer

OK, I get it!  It's to turn the fan ON, not to turn it off!!  That makes a whole lot more sense to me, Colorado's humor not withstanding.

And is there a second radiator fan assembly available from anyone?

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  • Forum CEO
FWIW, I did the same mod on my dear departed '86 and it worked great for when you got stuck in traffic. Switch the fan on BEFORE the motor gets hot. It seems to help if you get a jump on the heat.

Yea that was the whole idea, turn it on before it gets overheated, next time I am tuning my PC2 or somthing I just switch on the fan, or before I overheat in the stop and go traffic. It seems to be much cheaper than the $40 replacement thermo switch.

I would like to point out that having the fan on at speed is counter productive since it sucks air into the radiator from the side vents, once you get going at speed the air goes from the the wheel well and out thru those vents the opposite way!  Having on the fan would just work against the the natural flow when your riding at speed.

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  • 3 months later...
  • 2 weeks later...
Guest VFRrider800
I'm a car audio installer so don't think me dumb for asking this. Is the switch a ground trigger? Is that why there's the "extra" ground wire? Please explain. Thanx
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  • Forum CEO

Yep that all it is, the OEM switch that turns on the fan grounds the circuit when it gets hot and the fan motor starts, They way I have it wired it will work if the thermo switch gets hot or if I turn it on manually.  

So in other words it if the manual switch is off it will still be able to turn on the fan if the thermo switch kicks in.

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  • 5 months later...
I like this idea!  The link for the details on how to wire in this auxilary switch for the fan doesn't work.  Knowing full well that I am electronically challenged, can anybody fill me in on how to do this little mod?
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  • Forum CEO

it is super simple really, all your really have to do is ground the wire that goes to the thermo switch.  that is how the fan turns on.

So I have a wire extention from the fan wire to the thermo switch,  then I splice into that extention labled male and femal connectors.  Then I run it to a manual switch from there to a ground.

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Guest heavyio

I love it but I have no clue where anything is..  

I will try this mod when I get back from my vacation.  I hate sitting on a 225 bulbus pod.  

Until I rode my 03 VFR I didn't know my NU7$ couls sweat so much or this part  

)!(  

ha ha ha ha

Heavy  :wheel:

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  • 6 months later...
Guest kerplode

I'd like to suggest a modification to this procedure.  The rad fan is a fairly high current load (by itself on a 20A ckt in the VTEC), and I would not trust a simple switch to handle it without getting hot.  A better, but slightly more complicated, method would be to use a small automotive relay (30A rated) to switch the fan motor to GND.  Your dash switch would then activate the relay, and the relay switches the fan on.  I think that this is a much more robust way to approach the fan bypass mod.

I'll attach a simple schematic.

md

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Guest kerplode

That's cool...As long as the rating of the switch is equal to or greater than the rating of the fuse, everything should stay happy.

The original procedure didn't specify that a high-current switch was required.  I didn't want people to get the idea they could just run down to the Radio Shack, pick up a 0.5A small signal SPST switch and do a direct wire bypass on the fan.  Such a setup would quickly fail, and could potentially cause a fire.

md

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  • 9 months later...
Guest Samuel

I was thinking about doing the same thing to mine. Over the summer me and a couple of friends rode out to Tennessee and hung out at The Dragons Tail for a day. We decided to go over to Gatlinburg and got stuck in some "Fall Festival". We got stuck in traffic for over 2 hours. My nut's were hard boiled by the time we got out of that mess.

Samuel

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  • 1 year later...
  • Member Contributer

I'm thinking of modifying this slightly... to turn the fan off. On the way home yesterday 104 degrees + 80mph = 230 degrees of engine temp. Since the fan was running the whole time fighting the airflow I think it needs some attention.

Has anyone made the fan spin backwards? Probably more trouble than its worth, but pulling the air in with the fan so its more "comfortable" is silly... The left shin is rather warm anyway.

HS, can you repost your pics? I know its been a while... Thanks

Edited by thereisnospoon
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