UK Car Repair: W Reg Renault Megane Immobiliser issue, renault megane, issue question

Question
QUESTION: Intermittently my immobiliser will just not turn off.  There appears to be no rhyme or reason, occurs in all weathers etc.  I have to leave it from 5 minutes to up to 2 hours, it will then just turn over and start.  Similar issue is that sometimes when I turn the key, a loud fan in the engine turns itself on and the engine will not start until left for upto 2 hours.  Please help!

ANSWER: Electronic faults like this need to be diagnosed in person, there are so many things to consider.  Have you changed the batteries?

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QUESTION: Yes, batteries changed and also have a new key - has made no difference whatsoever.  AA have also been called out, but of course by the time they get to the car, the immobiliser decides to turn itself off and start!  They can't find anything wrong with it

Answer
You may have to take the car to a garage with a scanner that can set the security system. Sometimes it can be done by using the key to unlock & lock the drivers door holding the key in each position for a few seconds,then quickly doing the same with the remote.