Radiator fans not starting

Hi All,

I’m having a bit of a issue with my S4R (996). The rad fans will not start when the coolant gets to 102c. I’ve tested the fans and they work perfectly fine as they start if I disconnect the plug from the rear coolant sensor.

I’ve contacted the garage that I bought the bike from as it’s still under warranty and they have been very helpful as I live so far away from them, they have sent new parts for me to fix it. I’ve replaced the rear coolant sensor as I assumed that it had failed as it was also running a little rich when it was warmed up. The bike is now running perfectly, but the fans still won’t start when the coolant gets to 102c. If I unplug the connector to the sensor the fans start straight away.

I assume I can rule out any issue with a relay as they start.

I’ve traced all the wiring back to the ecu and it’s all testing ok.

Has anyone encountered this issue before, as I’m all out of ideas?

Thanks for your help in advance.

Adam