Had exactly this problem on my 2001 KV6 R75 and had to remove fuse to stop the battery going flat when engine off (fan still roaring away). Relied on the IPK diagnostic to monitor coolant temp, switching engine off in stationary traffic if necessary. Eventually replaced complete fan assembly while having the belts done. Back to normal now.
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Originally Posted by T-Cut
A failed temperature sensor or connection does indeed activate fan operation irrespective of any logical need. This is a safety measure and the ECU 'assumes' the engine could be overheating during the event. However, this fan operation will stop after ignition off. It may well run on for up to ten minutes after, but it will stop. Continuous running 'forever' is a different issue.
The fan system has a permanent live fead and is switched on the earth side of the motor. Any fault that would cause this to happen will result in the continuous fan operation without the ignition. Examples are a 'stuck-on' relay, a worn through wire short and shorting in the fan circuit connectors behind the LHS wing liner.
From the described circumstances, I'd suspect the lost sensor signal. It's likely the fan running hasn't been left long enough to auto stop after ten minutes. First check is to clean and reset the sensor connector located between the heads.
TC
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