Flaya, are you the original owner? If not, maybe the previous owner went into the ECM settings and made adjustments to the fan settings. I would start troubleshooting by re-flashing the ECM with a known-good ECM eeprom profile for your make/model. At least that way, you'll know you're starting off with factory settings with regards to sensor parameters, and then go from there. If you're running custom fuel/timing maps, you can save them off separately prior to the eeprom flash and re-load them afterwards to get your custom tune back. If you don't start with an eeprom re-flash and the parameters are out of spec, you'll likely end up on a wild goose chase and possibly make things worse by swapping or tweaking things unnecessarily with the risk of introducing new problems along the way.
If your fan keeps running after you do an eeprom re-flash, then I would definitely look at your engine temp sensor as bad or flaky. If you're handy with a volt/ohm meter, you can look at chapter 4 of the service manual to check your engine temp sensor for proper operation.
From the manual: "Cooling fan actuation is controlled by the ECM. With key ON, the fan turns on when engine cylinder head temperature reaches 220° C (428° F) (per the engine temp sensor) and shuts off when temperature reaches 180° C (356° F). With key OFF, fan turns on when engine temperature reaches 170° C (338° F) and shuts off when temperature reaches 150° C (302° F)."
Based on this, either (1) your ECM is faulty, (2) the ECM eeprom settings have been messed with and need to be restored to factory setting (see advice above), or (3) your engine temp sensor is faulty. All three are directly responsible for the fan operation. After reviewing the manual troubleshooting and theory of operation, I don't see any other contributing factors or components on an otherwise healthy bike that would cause your fan to run continuously.
The only other possibility that I can imagine would be a short in your wiring between the engine sensor and the ECM, between the ECM and fuse/relay, or between the fuse/relay and the fan itself. Personally, I have seen insulation on the ET sensor wiring rubbed bare on several Buells, including my own where the wire comes up from the sensor and runs next to the frame. My remedy is to wrap the bare spot with electrical tape and then cover the wire with a short piece of small vacuum hose that has been slit lengthwise to allow it to slip over the wire and protect it from further chafing.
Good luck and come back to let us know what you find for the benefit of others who might experience the same problem. :)
Thanks guys. So since 5pm this afternoon I've been trying to work out what could have gone wrong...
I've disconnected the temp sensor, fan stays on, I've chased wires, nothing grounded, long story short, it's the ECM. When I unplug one or the other plugs going to the ecm the fan stops.
I reset the eeprom, no different. So, While I was at it, I updated the good ECM to the race map, can't wait to ride it tomorrow if it's not raining.
Thanks for your help.
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