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Discussion Starter #1
I've had my '98 ST2 for a little over a month. Today I rode to a close town about 30 minutes away and got caught in stop and go traffic. The outside temp was in the low 80's and while sitting the engine temp climbed to 212 degrees! Once I was on the open road it dropped down to 167 degrees. When I got home I noticed that the fan was not coming on once the temp was high so I started digging around. I haven't found any blown fuses but not sure where to look either. I also found a lose wire on the right side up near the tree. Can anyone help?
 

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Viper,

The fan is controlled by the ECU and for some reason they are programed to come on at a very high temp. My ST4s comes on at 227 degrees F. So there may be nothing wrong with the fan. If your hoses and radiator cap are in good shape the pressure will keep the cooolant from boiling. Many of us have added a switch to manually turn on the fan whenever we like. It gives you something to do in traffic.

The connector looks like an OEM unit. You may be able to identify it by looking at the wiring diagram in the back of your manual. Is your neutral light working? I'll bet the connector has become unplugged somehow. If you remove some of the fairing you should find the other end.

Consider purchasing the service manual from www.desmotimes.com. It's a big help.

Jeff in Colorado
 

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The fans on my ST's all came on when the temp gauges reached 217* F, so the temps on your ST2 were not unusual.
 

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Yep, as stated above..."normal". The only way to keep the temps under 200 is a manual fan switch or a different thermostat (I've heard of the thermostat thing but have no experience with it. I DO have the manual fan switch by Desmo Times though).
 

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Just adding a "me to" to the discussion. My fan comes on at 217. Living in Texas I've added the Desmo Times fan a manual switch to keep the temp down in stop and go traffic.
 

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The FIM 161 chip turns my fan on at 190. I did put LT"s larger fan on, just never installed the switch. I ride mostly in the country, I try to avoid city traffic.:p
 

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I have a 2002 ST4s and it can get hot too. With the rear cylinder being right under the seat, it can cook your privates in stop n' go traffic. It used to get hotter faster when I first got it, but I flushed the coolant and coolant tank a few times (coolant was almost black!) I wire brushed all the bugs and road gunk out of the radiator. Then, I put fresh coolant (mixed with water percentage wise according to the service manual) with a bottle of a product that that's supposed to keep the coolant ten degrees cooler (I checked to make sure it was compatible with our Ducati engines.) The bike seems to run somewhat cooler than it did before, but in stop and go traffic it will heat up, just takes longer.(Thank goodness for California's lane splitting laws.)

One thing I also did was take the fairing covers off and clean all oil and sludge and road debris off the engine the previous owner neglected to do. I think that crap may have had the effect of holding heat in the engine area too.
 

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Discussion Starter #8
Thank you for all the quick replies. I took the advice in installing a by-pass switch on the sensor. Not sure if this is normal but when I kick on the switch, the fan does not come on right away and seems to be sporatic. Is this normal for the ECU to not engage the fan right away or did I miss something? All I did was install a two-post switch to the two wires on the sending unit's connector to jump across the connection.

Also, I had the fairing off while installing the switch and did NOT see a place for the connector to go. Is there a possibility in it going to something that did not come factory on my bike? My neutral light is working. It is a very large size red and black wire.
 

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Viper,

I suggest you consider the High Velocity Fan Kit sold by www.desmotimes.com. The kit includes a fan blade that is much more efficient than the OEM fan and a wiring kit and switch for manual control. The kit runs power directly from the battery to either of the the purple wires using a fuse link and a very trick switch. This way your sensor still works if you forget to hit the switch.

Something is wrong with the wiring change you have made. I have no logical reason, but I don't like including the ECU in any wiring changes that I make. My rule is don't play tricks on your ECU. No one of us really knows what goes on in there.

BTW, the search function on this forum and on the Halls of Wisdom section contain pages on this topic.

Jeff in Colorado
 

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The red/black wires / connector sounds like the one that comes from the RR to charge the battery. Maybe someone put an aftermarket RR on your bike, and left the old one bolted in place?

Also note that if you place 150 Ohms into the temp. connector that feeds the ECU, it should turn the fan on. I think it gives the equivalent of the thermister at around 230F. (You can verify this by plugging the 150 O. into the readout connector, and it will indicate the temp it thinks it's looking at .)
Shorting this connector will make the ECU think that the engine is overheated, and I'm not sure what it does at that point...
 

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Discussion Starter #11
The kit runs power directly from the battery to either of the the purple wires using a fuse link and a very trick switch
Could you tell me where the wiring kit is supplying power too? I already have the switch mounted and could re-adjust the setup for now to directly power the fan to see if that works. I'm thinking I can put a 5amp in-line fuse and the switch between the battery and power to the fan. I just need to know what purple wires you're referring to and if that will work.
 

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Discussion Starter #12
Disreguard further information on the fan wiring schematic. I did some further investigation on the forum and found the information that I was lacking. I have now wired the switch at a 12v power to the fan through the ignition controlled power and all is working great. Thanks again for the information.
 
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