Engine cooling fan run on

High there! Can anyone suggest cause of engine fan running continiously. Sometimes after journey, switched off engine and fan would run on, expecting it to shut down within 5-10 minutes. This would be still running 30 minutes later and continue to flattern battery. I have to remove earth cable from battery to stop this. when reconnected the fan will start up again, even when engine cold. Following a journey, switch off engine and the fan is silent, everything seems O K again, but on experience this condition returns again sooner or later. I have checked coolent sensor on cylinder head and expected when unpluged would create open circuit and stop fan , is there something I am missing ? I would be gratefull if anyone can shed any light on this problem please, regards Alan Rendall.

suspect sticking relays in the fan control box.

Mine does this - when it does I just pull the big 80 amp fuse in the fuse box, and whack it back in when I need to use the car - typically the problem goes away almost immediately when I put the fuse back.

No idea why but a sticky relay makes sense - I've been meaning to get an auto-electrician to look at it but it needs to be happening at that precise time!

When this occurs, try putting the AC on for a while, then whack it into ECON mode - this often works for me with the fan turning off a few seconds later.

Next time it happens try pulling the connector off the Trinary switch on the AC pipe the one just above the clutch reservoir.
High pressure in the AC will cause the fan to run but I don't think it should continue with the ignition off.

Worth trying though as it is a simple test