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Discussion Starter #1
Cooling fans are inopt. Fuse is good. Fans would not operate with fan relay connector (M lead) bridged. Checked voltage. Only getting five volts at the fan relay connector (M lead)? Battery is fully charged. Knew it wouldn't make a difference but I also did a voltage check with engine running. Still only five volts?
 

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I think I might have found the problem? Haven't removed temp sensor for full range test yet, does anyone know off the "top of their head" if 3.7 Kohm is max resistance for the coolant temp sensor? Mine is reading 6.6 Kohm cold. Guessing about 15 celsius. Didn't mention earlier I have 2007 F4
 

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Discussion Starter #4
Thanks Noel
Removed the temp sensor and ran the test up to 230 degrees around 90 celsius. At that temp it was showing 0.3 ohms which is about where it is supposed to be. It cooled down to 4.2 ohms. Didn't see the 6.6 again.
 

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Swap the leads between the 2 sensors on the radiator and motor, the one on the rad does the display, the one on the motor supplies the ECU, see what that does on your display.
Fan relay is operated by the ECU, and is sitting just on top of your fuse box on the R/H side of your bike. The realy is the same as used for indicators ...etc situated on the front of the bike if you wanted to swap one out to test.
 

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Were you able to get the fans to work? Same thing happened to my F4. I tried to bridge the relay but did not work. So what I did was I ran a wire from the fan directly to the battery and the fan worked. Now you just need to determine wether it is the relay or temp sensor. Most likely it is just the relay. Good luck.
 

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Cooling fans are inopt. Fuse is good. Fans would not operate with fan relay connector (M lead) bridged. Checked voltage. Only getting five volts at the fan relay connector (M lead)? Battery is fully charged. Knew it wouldn't make a difference but I also did a voltage check with engine running. Still only five volts?
Hi Kent
I've got a 2006 910S with single fan. Notice u mention "fans" so yours might be later/different model. FWIW, I had similar problem recently. Noel, Donsy et al all gave invaluable advice. However, in my case it was corroded contacts on the engine temp sensor. :drummer: I cleaned them up and the problem fixed. In my case, the fan wouldn't kick in automatically at the set temperature range approx 94C. However, a few steps along the way:
- you've already checked the fuses/ran battery direct to the fan, the resistences of the sensors at various temps etc
- I checked that my SPU was the "black"-back variety and NOT the "blue" (see the sticky thread). Spent weeks going crazy looking for the 'fan relay', which is an ICU digital type inside the SPU
- when testing by bridging the engine temp sensor (M lead) ensure ignition is ON but motor not running, AND the emergency/kill switch is ON. I initially missed doing the latter and spent weeks chasing my tail
- cleaned the contacts on both the engine/radiator temp sensors both on the switch itself and the plug-in sockets
- i installed a manual over-ride switch feeding direct battery via fuse link to the fan

good luck, cheers Claudio
 

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Discussion Starter #9
Thanks Bill for the reply
Didn't have a chance to work on the bike again till today. No luck yet. Both the temp sensor and fan relay are working according to specs. Today I reinstalled the sensors, prepped and then ran the engine up to 223 degrees on the display checked the relay and found zero ohms resistance. It's closing. Ran the engine again to 223, then checked voltage and having followed Claudio's advice by cleaning connection points I was now getting 6 volts. Repeated the same procedure with the temp sensor, 0.3 ohms. I think that clears those two.
 

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Discussion Starter #10
Thanks Claudio
I hear what you're saying about the kill switch. In the scramble run test while the engine is at test temp I once forgot to turn the key on. Haven't given up yet but might have to do the over-ride. Going to ask Donsy some questions
 

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Discussion Starter #11
Donsy,
To make sure I understand. You're saying to switch the leads between the temp sensor on the radiator and the fan relay on the engine? Or is there an engine mounted temp sensor I'm not seeing? What would I be looking to see on the display when the leads are switched? There's a small black plastic box plugged into a lead connector on top of my fuse box is that the ECU?
 

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Hang on there mate.

Donsy,
To make sure I understand. You're saying to switch the leads between the temp sensor on the radiator and the fan relay on the engine? Nope

Or is there an engine mounted temp sensor I'm not seeing? Yes

What would I be looking to see on the display when the leads are switched? Just a small difference in temps, if it's a very big difference, or no display, the sensor or connection is bad.

There's a small black plastic box plugged into a lead connector on top of my fuse box is that the ECU? Nope[/quote]

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Firstly, download the workshop manuals for your bike.
You will then see that the ECU is the big box under your seat, the little black box on top of the fusebox is the fan relay.
Check the fan fuse first.
Then go back and read what I said before, your bike has two temp sensors, one on the radiator and one just behind it on the motor.

If your bike is warmed up past 97deg, and the fans are not running, then a quick check is to swap the plugs on the 2 sensors, fan still not running, then check the relay next.
You have spare/similiar relays on the front of the bike, next to the headlight, you can use these to verify the relay operation.

Remember this, the temp sensor on the radiator is for display, the one on the engine control's the relay, amongst other things, this is very important to remember.

Secondly, you have an F4 which is completely different in wiring to the Brutale/B4's.

Good luck.
 

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Discussion Starter #13
Hello Donsy
Pulled the ECU for the fan relay you described as setting just on top of the fuse box. Huge corrosion issue! The rubber band mount was covering the connection point between the ECU and the connector, trapping in moisture. Large amount of rust and whitish blue powder.
 
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