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Are you SP1 or SP2?
I have an extra OEM SP1 sensor you can have...
The sensor mounted on the thermostat housing is the same on both SP1 or 2 so any temp sensor would do.

Since this sensor is working based on variable resistance value caused by temp changes, Hanberg is right I believe. If any of it's 3 wires had a poor connection, the temp indication should be lost.
My guess is just a faulty sensor.

But still....one can never be too sure of anything when it comes to electrics.

Swap the sensor with one that you know it works and see what happens.
 

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Also,
You could pull your sensor, put it in a pot of water on the stove and check it's resistance as the water heats up.

I don't know what value is needed at what temperature but it may show a temp range were the ohms don't change or something.



Sent from Motorcycle.com App
Page 384 on the manual

 

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Discussion Starter #9 (Edited)
Crap, I thought it was the one in the radiator?

So, Im not that much into the function of the cooling system. I know my mechanic checked the thermostat when he had the bike for valve-check.

And I just pulled the left fairing, dried drops of coolant down the generator-cover, and the reservoir was pretty much empty. Filled to max and went for a ride, temp. stable around 77-78 while riding, and rose nicely to 103 when parked and dropped nicely when the fan came on. There were coolantspray again.
So I guess there is a leak somewhere, will have to check later
 

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Crap, I thought it was the one in the radiator?

So, Im not that much into the function of the cooling system. I know my mechanic checked the thermostat when he had the bike for valve-check.

And I just pulled the left fairing, dried drops of coolant down the generator-cover, and the reservoir was pretty much empty. Filled to max and went for a ride, temp. stable around 77-78 while riding, and rose nicely to 103 when parked and dropped nicely when the fan came on. There were coolantspray again.
So I guess there is a leak somewhere, will have to check later
SP1's use the more simple thermal switch mounted into the left radiator to switch on the single fan, while the SP2 uses a sensor mounted into the thermostat housing which sends a signal to the ECU to switch on the dual-fans via the fan control relay.

Your leak could be from a loose hose clamp, or a possible crack in the left radiator.
I've heard comments from SP1 owners where the radiators are prone to develop cracks due to only two mounting bolts vs. three on the SP2.
Check near the mounting tabs if there is coolant residue nearby.

I had a similar leak problem with my SP2 due to a puncture in the upper radiator tank by the prior owner, who repaired the puncture with JB Weld.
That repair didn't hold due to the radiator flexing with each heating/cooling cycle, and I found coolant dripping down my radiator and onto the ground.
Was able to have the puncture welded and pressure tested.
 

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Discussion Starter #11
So time for an update.
I just fitted a new temp.sensor in the thermostat-housing. Fired the bike up and let it idle for 15 minutes (outside temp about 20c) an only got up to 94-96c. But still change up and down 4-5c. While idleling from cold it would go 37-38-39-37-38-39-38 etc all the way up, and hover along time around 78-83c.
Fan never came on, even though it idled for 15min. So do I need to pull the bike completely apart and start looking at wires?

And when I had the thermostathousing off to change the sensor, it would rattle when shaken? My mechanic had it apart when he had the bike in the winter to check it - and Ive had the problem since it was back together?
 

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Discussion Starter #12
Well took the thermostat apart and boiled it to check it, its OK.

Taken the wires apart looking for bad connections, didnt really find any. Hooked it up besides the bike and put the temp.sensor in a pan of hot water. Water is about 55c.
With the pan just sitting on the ground, the gauge will show 35c. When I rest the pan on the footrest, it will rise to the correct temp (checking water with kitchen thermometer)...

Must be a bad ground somewhere?
 

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Puzzling for sure.....

Did you follow the directions that Makis posted for the temp sensor about testing the Ohm resistance at specified temperatures in the pot of hot water?

 

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Discussion Starter #15
Yes boiled the thermostat in the kitchen to check that it opened correctly, and brought hot water into the garage at put the entire thermostat with sensor in it and connected it to the bike. Compared temp on the gauge with a kitchen termometer in the water and they went along nicely

And this is with a brand new, 45£ sensor - and I got same result with the old one, so "unfortunately" the sensor is OK.
 

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There is an earth connection somewhere thereabouts, i can't tell you exactly where but it is a brass ring connector that sits under a bolt, make sure you clean the connection up, it will give similar problems to the ones you describe.
 
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