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Running fan on AC

Here's what I ended up doing. Got a 25 amp/ 50 volt bridge rectifier and wired in the ac input side of the rectifier to the yellow wire out of the stator and the power in to the fan to the dc out put side of the rectifier. The fan doesn't run quite as fast as when it powered from the battery but I rode three days of tight single track with some good hills and lots of clutch work and didn't get hot once, and the battery had lots of juice to fire up on the e start. Seems to work great so far.
 
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Spal Fan Controller Setup

Ok, I got the handlebar switch mounted. Turns out my Vapor computer won't run properly off the AC wire either (false and sporadic tachometer readings resulted). So I now have the Vapor and the fan controller running off DC. Neither take much juice to run. The controller takes only 0.2 amps to function.

Not a particularly cheap route to go, the way I have it. But, here's what I've got into it:

Vapor computer ~$80
Additional temp sensor (replaces the air bleed screw on the head for the cooling system)~$40.
Factory Fan kit ~$135
Spal fan controller ~$80
Handlebar switch ~$16

Note: You're supposed to be able to splice into almost any existing temp sensor to work with the fan controller. I tried it with the in-line hose mount sensor that comes with the Vapor, but the controller didn't play nice with the shared sensor. Thus, the additional sensor.

Another note: You can save a grip a cash if you just buy the fan only from Spal, instead of the fan kit from KTM. If you're running a 2005 'berg the thermo switch that comes with the fan kit won't thread into the radiator (cause there's no threaded collar in it). That makes it, and the other wire harnes that comes with the kit useless. The only other useful part of the kit (other than the fan) are the mounts.

Anyway, I have the controller set to turn on the fan at slow speed (50%) at about 190 degrees C and the high speed (100%) at about 235. Whether there is actually any difference in fan speed between the two settings (as LeFrog suggests) I haven't yet determined.

Here's some pics:
 

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RE: Spal Fan Controller Setup

For anyone actually wanting to try the SPAL fan controller it does actually perform to its claims. I rode today and had it sitting at idle afterward to bring it up to the low speed setting and then to the high speed setting, and there was a very obvious difference in fan speed between them. The settings are about 40 degrees apart.
 
Fan

I installed a new KTM fan on my 525 a couple of years ago. Their fan housing has a weird flap on it to let air through when the fan is not running. Once that flap gets old it doen't work like it should.

It lets the fan draw air through it. Once this happens the fan doesn't draw air though the radiator like it should. The fan runs and runs. That pulled the battery down everytime.

Later I found out that even small air leaks will give the same result.

Check to see if your fan is running all the time. Even when you think that it should not be running.

Other than that the KTM guys use the cut off switch alot. They call it a thumb-o-stat. Again it can be used when the bike is hot but you on the verg of enterning a go fast section.

I will be putting a thumb-o-stat on my berg when I do the fan on it. Its a good idea.
 

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